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Would you like to inspect the original subtitles? These are the user uploaded subtitles that are being translated: 1 00:00:01,400 --> 00:00:03,960 NARRATOR: Satellites above an iconic American city 2 00:00:04,120 --> 00:00:05,600 make an alarming discovery. 3 00:00:06,880 --> 00:00:10,400 Vast ruins stand out in the middle of the Saharan Desert. 4 00:00:12,000 --> 00:00:15,280 Drones uncover a puzzling stone mystery perched 5 00:00:15,440 --> 00:00:16,800 high in the Andes. 6 00:00:18,280 --> 00:00:19,280 And a massive, 7 00:00:19,440 --> 00:00:23,160 modern metropolis in the Mongolian desert totally deserted. 8 00:00:23,320 --> 00:00:24,840 - Where is everybody? 9 00:00:27,320 --> 00:00:29,800 NARRATOR: Everywhere we look on our planet, 10 00:00:29,960 --> 00:00:31,400 there's evidence of the past. 11 00:00:32,040 --> 00:00:37,680 In nature. In buildings. In relics. 12 00:00:39,080 --> 00:00:44,240 Each holds a mystery that technology now allows us to see from above. 13 00:00:47,400 --> 00:00:49,720 What new secrets are revealed? 14 00:00:57,320 --> 00:01:00,680 Across the globe, more than half of the world's population - 15 00:01:00,840 --> 00:01:05,040 4.4 billion people - live in cities, each full of hidden 16 00:01:05,200 --> 00:01:09,440 stories and secrets that are best revealed with a view from above. 17 00:01:11,480 --> 00:01:13,800 Flying high above New York City, 18 00:01:13,960 --> 00:01:17,120 cutting edge technology discovers something shocking. 19 00:01:19,520 --> 00:01:21,680 InSar satellites - designed to detect 20 00:01:21,840 --> 00:01:25,160 variations in the earth's surface - uncover an alarming increase in 21 00:01:25,960 --> 00:01:29,360 the rate of a bizarre and disturbing phenomena called 'subsidence'. 22 00:01:31,680 --> 00:01:34,960 - Subsidence is a geological term for the downward vertical 23 00:01:35,120 --> 00:01:37,560 movement of the Earth's surface. 24 00:01:37,720 --> 00:01:40,400 Basically it's sinking. - Hold on, did you say sinking? 25 00:01:42,520 --> 00:01:46,160 So New York City is sinking? 26 00:01:46,320 --> 00:01:49,000 - And they found this out - from the sky? How's that work? 27 00:01:50,080 --> 00:01:52,680 - InSAR satellites are especially good at detecting 28 00:01:52,840 --> 00:01:54,240 and measuring subsidence. 29 00:01:54,400 --> 00:01:57,720 With each pass over the earth, they track ground deformation 30 00:01:57,880 --> 00:02:01,760 and changes that occur gradually over months or years. 31 00:02:01,920 --> 00:02:04,400 - They can cover huge areas, making them 32 00:02:04,560 --> 00:02:07,360 ideal for urban environments like New York. 33 00:02:07,520 --> 00:02:10,520 - Subsidence has been occurring where New York City now sits 34 00:02:10,680 --> 00:02:12,760 since the end of the last ice age. 35 00:02:12,920 --> 00:02:16,800 As the ice sheets retreated, the land once covered by the ice, 36 00:02:16,960 --> 00:02:19,640 north of the city, began to rise up and the land just 37 00:02:19,800 --> 00:02:23,360 south of the ice, where New York City is today, began to sink. 38 00:02:23,520 --> 00:02:28,120 That slow response to melting of the ice sheets continues today, 39 00:02:28,280 --> 00:02:32,320 at a rate of about 1 to 2 millimetres every year. 40 00:02:32,480 --> 00:02:35,320 - Okay, so what's the big deal? 41 00:02:35,480 --> 00:02:38,320 NARRATOR: Tracking from the skies, the satellites over New York 42 00:02:38,480 --> 00:02:43,800 find parts of the city are sinking at a pace of 4mm a year - 43 00:02:43,960 --> 00:02:47,760 that means the Big Apple is going down far faster than expected. 44 00:02:50,000 --> 00:02:53,440 But what is behind this terrifying drop? 45 00:02:53,600 --> 00:02:56,000 What kind of forces can sink a city? 46 00:02:58,840 --> 00:03:01,720 Could this be caused by sinkholes? 47 00:03:04,240 --> 00:03:07,040 - Over the past decade, we are seeing more and more of them 48 00:03:07,200 --> 00:03:08,560 across the world. 49 00:03:09,840 --> 00:03:12,840 And they're getting bigger, deeper and a lot more dangerous. 50 00:03:15,200 --> 00:03:18,560 - Sinkholes tend to form in cities for one of two reasons: 51 00:03:18,720 --> 00:03:21,000 either a section of a street collapses 52 00:03:21,160 --> 00:03:24,880 because of a water main break or an old pipe giving way or, 53 00:03:25,040 --> 00:03:28,240 you get changes to natural water-drainage patterns. 54 00:03:28,400 --> 00:03:32,160 - In recent years, more and more sinkholes have left enormous 55 00:03:32,320 --> 00:03:36,200 gaping pits in downtown Manhattan - the middle of East 89th 56 00:03:36,360 --> 00:03:39,840 Street on the Upper East Side and Riverside Drive on the 57 00:03:40,000 --> 00:03:44,120 Upper West Side being two examples that happened only days apart. 58 00:03:44,280 --> 00:03:46,560 - It's believed that these new multi-foot-deep 59 00:03:46,720 --> 00:03:50,320 depressions are the result of the city's deeply outdated 60 00:03:50,480 --> 00:03:55,560 underground infrastructure, which has an average age of 66 years. 61 00:03:55,720 --> 00:03:59,280 - And with 7,000 miles worth of water mains, 62 00:03:59,440 --> 00:04:03,160 that's a lot of old pipes posing silent threats. 63 00:04:03,320 --> 00:04:05,080 - So could the increasing size 64 00:04:05,240 --> 00:04:07,920 and frequency of sinkholes be bringing down the city? 65 00:04:08,080 --> 00:04:09,280 - Unlikely. 66 00:04:09,440 --> 00:04:12,880 Deep and dangerous as they are, these sinkholes alone are not 67 00:04:13,040 --> 00:04:15,600 enough to take down a city the size of New York. 68 00:04:15,760 --> 00:04:19,160 - So what is happening in New York City? 69 00:04:19,320 --> 00:04:22,000 NARRATOR: Perhaps there's a clue in another sinking city 70 00:04:22,160 --> 00:04:26,720 almost 12,000 km away, Shanghai, China. 71 00:04:28,720 --> 00:04:32,200 - China's most populated city has dropped more than six feet 72 00:04:32,360 --> 00:04:34,040 since 1921. 73 00:04:34,200 --> 00:04:37,000 The result has been devastating flooding in the city 74 00:04:37,160 --> 00:04:39,000 and getting worse every year. 75 00:04:40,760 --> 00:04:45,480 - The problem stems from Shanghai's rapid 19th century growth, 76 00:04:45,640 --> 00:04:49,080 stretched to supply factories and drinking water to a population 77 00:04:49,240 --> 00:04:52,960 that by 1900 had tripled to more than one million. 78 00:04:53,120 --> 00:04:57,000 Groundwater that had supported the Chinese trading port quickly 79 00:04:57,160 --> 00:04:58,520 became strained. 80 00:04:58,680 --> 00:05:00,200 - And it kept going. 81 00:05:00,360 --> 00:05:02,640 The problem got so bad by the 1950s 82 00:05:02,800 --> 00:05:07,920 and 1960s that the ground was sinking by four inches a year! 83 00:05:08,080 --> 00:05:10,720 - The government took action in 1963, 84 00:05:10,880 --> 00:05:14,840 banning the overuse of wells but the decline continued 85 00:05:15,000 --> 00:05:19,240 - by the mid-1960s the city had sunk about 16 more inches. 86 00:05:19,400 --> 00:05:22,240 And it's only going to get worse! 87 00:05:22,400 --> 00:05:25,360 Official projections say water levels could rise several 88 00:05:25,520 --> 00:05:29,680 inches by 2050, threatening waterfront areas. 89 00:05:29,840 --> 00:05:32,560 NARRATOR: Could this be happening to New York City? 90 00:05:32,720 --> 00:05:36,240 Is the Big Apple's drinking causing its sinking? 91 00:05:36,400 --> 00:05:38,800 Is the loss of groundwater the problem? 92 00:05:39,960 --> 00:05:42,160 - It's unlikely that this is just a groundwater thing. 93 00:05:42,320 --> 00:05:44,760 Groundwater management has been a part of New York City's 94 00:05:44,920 --> 00:05:48,880 infrastructure for decades - between 1996 and 2007, 95 00:05:49,040 --> 00:05:51,840 the city transitioned away from using any groundwater 96 00:05:52,000 --> 00:05:54,400 wells as part of their drinking water supply. 97 00:05:54,560 --> 00:05:58,240 - So, if it's not water going out maybe it's water coming in 98 00:05:58,400 --> 00:06:00,560 that's the problem? 99 00:06:00,720 --> 00:06:03,160 NARRATOR: The satellite view over New York City, 100 00:06:03,320 --> 00:06:07,240 shows that the areas sinking fastest are the edges of the city, 101 00:06:07,400 --> 00:06:10,280 where New York lies less than 2 meters above sea level. 102 00:06:11,480 --> 00:06:15,320 - Could the rising sea levels be pushing the city down? 103 00:06:15,480 --> 00:06:17,760 It's no secret that storms and hurricanes have 104 00:06:17,920 --> 00:06:22,440 increased in ferocity in the past decade with devastating results. 105 00:06:23,840 --> 00:06:28,480 - In 2012, Hurricane Sandy killed more than 40 New Yorkers, 106 00:06:28,640 --> 00:06:31,560 destroyed approximately 300 homes, 107 00:06:31,720 --> 00:06:35,520 and left tens of thousands of people without power. 108 00:06:35,680 --> 00:06:39,400 - In 2021, Hurricane Ida left more than a dozen people dead in 109 00:06:39,560 --> 00:06:44,040 New York City, many after they were unable to escape flooding basements. 110 00:06:46,040 --> 00:06:49,560 - In New York City, sea levels have risen a foot over the last 111 00:06:49,720 --> 00:06:55,480 100 years - that's a rate of about 1.2 inches per decade. 112 00:06:55,640 --> 00:06:59,120 - That may not seem like a large increase, the implications are huge. 113 00:06:59,280 --> 00:07:03,080 Sea levels are expected to rise anywhere from 8-30 inches 114 00:07:03,240 --> 00:07:04,440 by the 2050's. 115 00:07:04,600 --> 00:07:08,920 And as much as 15-75 inches by the end of the century. 116 00:07:09,080 --> 00:07:12,200 NARRATOR: Are rising sea levels destined to consume - 117 00:07:12,360 --> 00:07:15,320 and sink - New York City? 118 00:07:15,480 --> 00:07:19,680 - While rising sea levels are very much a threat, a recent study 119 00:07:19,840 --> 00:07:24,040 of 99 coastal cities around the world found that subsidence - the 120 00:07:24,200 --> 00:07:28,240 sinking of the ground - may pose a bigger problem than sea-level rise. 121 00:07:28,400 --> 00:07:29,760 Why? 122 00:07:29,920 --> 00:07:31,560 Because most cities surveyed, 123 00:07:31,720 --> 00:07:35,880 the land is subsiding faster than sea levels are rising. 124 00:07:36,040 --> 00:07:39,280 - So what's causing this increase in subsidence? 125 00:07:39,440 --> 00:07:43,600 NARRATOR: Perhaps a clue lies closer to home over 1000 km 126 00:07:43,760 --> 00:07:45,520 away in Chicago. 127 00:07:47,920 --> 00:07:50,640 - Scientists from Northwestern University in Chicago have 128 00:07:50,800 --> 00:07:54,320 discovered that increased temperatures underground is 129 00:07:54,480 --> 00:08:00,000 making Chicago's clay soil contract, causing the Windy City to sink. 130 00:08:00,160 --> 00:08:03,760 - What they discovered is that the heat escaping from basements 131 00:08:03,920 --> 00:08:06,760 and parking garages, sewers, tunnels, 132 00:08:06,920 --> 00:08:10,440 other underground infrastructure is actually shifting the landscape 133 00:08:10,600 --> 00:08:16,400 and its causing Chicago to slowly - but definitively - sink. 134 00:08:16,560 --> 00:08:19,480 - Much of Chicago was built on a glacial lakebed, 135 00:08:19,640 --> 00:08:22,160 which means very clay-ey soils. 136 00:08:22,320 --> 00:08:24,560 This type of soil can swell when heated - 137 00:08:24,720 --> 00:08:29,360 causing buildings built on top it to settle faster than normal. 138 00:08:29,520 --> 00:08:31,600 - The study showed that the ground could swell 139 00:08:31,760 --> 00:08:33,240 something like 12 millimetres, 140 00:08:33,400 --> 00:08:36,280 and the structures could sink something like 8 millimetres. 141 00:08:36,440 --> 00:08:38,640 And that may not sound like very much but 142 00:08:38,800 --> 00:08:42,040 those small changes can be devastating for buildings 143 00:08:42,200 --> 00:08:45,040 that are not designed for that kind of movement. 144 00:08:45,200 --> 00:08:48,160 - Nobody talks about this, but it's a real thing - 145 00:08:48,320 --> 00:08:50,840 scientists call it 'underground climate change.' 146 00:08:52,160 --> 00:08:55,760 - Could New York City be heating itself to destruction? 147 00:08:58,000 --> 00:09:01,880 NARRATOR: In 2023, researchers from the US Geological Survey 148 00:09:02,040 --> 00:09:04,960 and the University of Rhode Island decided to investigate. 149 00:09:06,800 --> 00:09:10,360 - What the team studied were InSAR satellite images collected from 150 00:09:10,520 --> 00:09:14,880 orbiting satellites that actually map subsidence all across the city. 151 00:09:15,040 --> 00:09:16,640 - The results showed as expected, 152 00:09:16,800 --> 00:09:19,840 that all of New York City as a whole is sinking 1 to 2 millimetres 153 00:09:20,880 --> 00:09:24,280 every year because of post-glacial relaxation. 154 00:09:24,440 --> 00:09:27,400 But, and this is the big part- they discovered that those 155 00:09:27,560 --> 00:09:30,480 parts of the city where big buildings are built on fill 156 00:09:30,640 --> 00:09:33,800 and sediment are sinking faster, up to 4 millimetres every year. 157 00:09:36,200 --> 00:09:39,600 - Could New York City just be too heavy?! 158 00:09:40,480 --> 00:09:43,160 NARRATOR: To test this theory, the scientists calculated 159 00:09:43,320 --> 00:09:47,760 the collective weight of more than a million buildings in New York City. 160 00:09:47,920 --> 00:09:49,520 - They estimated that 161 00:09:49,680 --> 00:09:55,880 NYC's buildings collectively weigh 1.68 trillion pounds - 162 00:09:56,040 --> 00:09:59,080 equivalent to roughly 1.9 million fully fuelled Boeing 747s. 163 00:10:01,840 --> 00:10:04,000 - And, that's just the buildings! 164 00:10:04,160 --> 00:10:09,800 That's not the contents, the people, the vehicles - all that other stuff! 165 00:10:12,000 --> 00:10:14,240 NARRATOR: To determine what part of the cities were bearing 166 00:10:14,400 --> 00:10:17,080 the most weight, 167 00:10:17,240 --> 00:10:20,720 the scientists divided the city into a grid of 100-by-100-meter squares. 168 00:10:20,880 --> 00:10:23,400 This allowed them to calculate the downward pressure 169 00:10:23,560 --> 00:10:27,760 caused by the weight of the buildings, across the whole city. 170 00:10:27,920 --> 00:10:30,520 - The research suggested that indeed, 171 00:10:30,680 --> 00:10:35,200 the weight of buildings is causing increased subsidence in those 172 00:10:35,360 --> 00:10:38,960 parts of the city vulnerable to this immense pressure. 173 00:10:39,120 --> 00:10:41,080 - The skyscrapers anchored to underlying bedrock 174 00:10:41,240 --> 00:10:44,480 in the upper parts of the city, not much of a subsidence problem. 175 00:10:44,640 --> 00:10:47,320 But, the hundreds of buildings sitting on spongy 176 00:10:47,480 --> 00:10:50,720 materials like clay and artificial fill on the lower lying 177 00:10:50,880 --> 00:10:55,120 edges of the city those are very prone to compression. 178 00:10:55,280 --> 00:10:56,840 - And it's important to remember that this is 179 00:10:57,000 --> 00:10:58,960 happening in a city where the sea level is 180 00:10:59,120 --> 00:11:04,160 projected to rise between 8 and 30 inches by 2050 - this extra sinking 181 00:11:04,320 --> 00:11:08,280 factor increases New York City's vulnerability to coastal storms. 182 00:11:09,680 --> 00:11:12,240 - The likelihood of parts of New York City eventually being 183 00:11:12,400 --> 00:11:15,200 permanently under water is inevitable. 184 00:11:16,360 --> 00:11:19,240 The ground is going down, and the water's coming up. 185 00:11:19,400 --> 00:11:22,400 At some point, those two levels are gonna meet. 186 00:11:22,560 --> 00:11:25,400 - Because we have rising sea levels and sinking 187 00:11:25,560 --> 00:11:28,800 buildings at the same time, this means that coastal flooding 188 00:11:28,960 --> 00:11:32,840 is gonna happen a lot faster than predicted by existing models. 189 00:11:33,000 --> 00:11:36,400 - It's a really scary projection - but, thanks to what we now know, 190 00:11:36,560 --> 00:11:40,120 cities like New York can much better plan and actually prepare 191 00:11:40,280 --> 00:11:44,960 for the long-term impact of sea level rise and coastal subsidence. 192 00:11:46,600 --> 00:11:50,280 NARRATOR: Revealing these hidden forces sinking New York City 193 00:11:50,440 --> 00:11:55,000 and other cities like it around the world before its too late is 194 00:11:55,160 --> 00:11:59,080 only possible with a high tech view from above. 195 00:12:04,760 --> 00:12:08,400 In the deep central Sahara, in the African country of Niger, 196 00:12:08,560 --> 00:12:13,480 a view from above reveals a sprawling, empty, ancient mystery. 197 00:12:16,600 --> 00:12:19,840 - What the heck is this place - it looks like a giant ant colony! 198 00:12:21,680 --> 00:12:24,880 - It looks like a small, fortified city - 199 00:12:25,040 --> 00:12:27,840 but slap bang in the middle of nowhere! 200 00:12:28,000 --> 00:12:30,960 - And it looks totally empty! 201 00:12:31,120 --> 00:12:35,200 - Abandoned cities are not unusual in the desert. 202 00:12:35,360 --> 00:12:37,680 - But most desert settlements found in this 203 00:12:37,840 --> 00:12:40,280 part of Africa are simple in their layout 204 00:12:40,440 --> 00:12:45,280 and scope - this one has fortified walls, watchtowers and passageways. 205 00:12:46,720 --> 00:12:50,400 NARRATOR: This unusual site is called the Ksars of Djado. 206 00:12:50,560 --> 00:12:55,040 Built between 800 to 1000 years ago, the architects of this site 207 00:12:55,200 --> 00:13:01,160 have long been a mystery - no one knows who built it. 208 00:13:01,320 --> 00:13:03,720 - It would have been an enormous undertaking, 209 00:13:03,880 --> 00:13:06,200 it would have required you know, a lot of elaborate planning, 210 00:13:06,360 --> 00:13:10,480 a lot of skill, a lot of time to create what is a spectacular 211 00:13:10,640 --> 00:13:14,040 fortress in the heart of northern Africa. 212 00:13:14,200 --> 00:13:17,720 - Why go to so much trouble to create a massive walled 213 00:13:17,880 --> 00:13:20,320 fortress like this, in the middle of nowhere? 214 00:13:20,480 --> 00:13:25,560 What was it meant to protect? Why are the Ksars of Djado, here? 215 00:13:25,720 --> 00:13:28,680 NARRATOR: A clue to this mystery may lie with another abandoned 216 00:13:28,840 --> 00:13:33,520 desert city almost 3000 km away in the Golan Heights where 217 00:13:33,680 --> 00:13:37,840 a view from above reveals the desert fortress of Nimrod. 218 00:13:39,200 --> 00:13:42,360 Like the Ksars of Djado, Nimrod lies empty 219 00:13:42,520 --> 00:13:46,160 and silent - another walled city left to crumble in the sand. 220 00:13:47,640 --> 00:13:51,760 - Dated as early as 30 CE, Nimrod was built to guard a major access 221 00:13:51,920 --> 00:13:55,760 to Damascus, a key centre of trade on the Trans-Saharan trade route. 222 00:13:55,920 --> 00:13:59,000 - The Trans-Saharan trade routes connected the Mediterranean 223 00:13:59,160 --> 00:14:03,440 coast to the West African savannah and the sub-Saharan region. 224 00:14:03,600 --> 00:14:06,760 - These routes were used to transport a variety of goods, 225 00:14:06,920 --> 00:14:10,880 including gold, ivory, salt, and slaves. 226 00:14:12,520 --> 00:14:16,400 - It's impossible to overstate the significance of these routes, 227 00:14:16,560 --> 00:14:20,200 in African history - really, in world history. 228 00:14:20,360 --> 00:14:23,400 They were also a major source of cultural exchange - 229 00:14:23,560 --> 00:14:25,360 traders brought goods, ideas, 230 00:14:25,520 --> 00:14:29,160 and technologies from one part of the world to another, leading to 231 00:14:29,320 --> 00:14:33,000 the spread of religions, languages, and other cultural traditions. 232 00:14:34,080 --> 00:14:36,760 - One example of a technology that was introduced to Africa 233 00:14:36,920 --> 00:14:39,920 through the Trans-Saharan trade routes is the camel, which was 234 00:14:40,080 --> 00:14:43,640 domesticated in the Middle East and brought to Africa by Arab traders. 235 00:14:45,200 --> 00:14:48,600 - The camel was an invaluable tool for trade and transport 236 00:14:48,760 --> 00:14:52,680 in the Sahara Desert, as it's able to travel really long distances 237 00:14:52,840 --> 00:14:57,480 across the desert with minimal water and can carry heavy loads. 238 00:14:57,640 --> 00:15:01,320 So the use of camels completely revolutionizes trade 239 00:15:01,480 --> 00:15:03,480 and transport in the region and it 240 00:15:03,640 --> 00:15:07,600 also facilitated the growth of the Trans-Saharan trade routes. 241 00:15:09,080 --> 00:15:12,240 - At the peak of the caravan trade, the average caravan was 242 00:15:12,400 --> 00:15:18,400 made up of 1,000 camels and some caravans were as large as 12,000! 243 00:15:19,520 --> 00:15:21,800 NARRATOR: Could this be why Djado is here - 244 00:15:21,960 --> 00:15:25,200 built as a fortress to protect a crucial trade route? 245 00:15:26,720 --> 00:15:29,640 - It's possible, because Djado was once smack in the middle of this 246 00:15:29,800 --> 00:15:33,960 complex network of trade routes all across Africa and the Middle East. 247 00:15:35,000 --> 00:15:38,840 - It's perfectly situated on this busy route, the Ksars of Djado 248 00:15:39,000 --> 00:15:42,680 would have thrived as a bustling and prosperous centre of trade. 249 00:15:43,760 --> 00:15:47,000 - The city was so successful, it swelled to be the biggest 250 00:15:47,160 --> 00:15:51,120 of its kind - it would have been a jewel of commerce in the desert. 251 00:15:51,280 --> 00:15:54,600 - It's sorta like an early, Saharan Las Vegas! 252 00:15:55,800 --> 00:15:59,360 - But, if the Ksars of Djado were so big and so strong 253 00:15:59,520 --> 00:16:03,600 and so prosperous then why did the city basically just disappear? 254 00:16:04,800 --> 00:16:08,600 NARRATOR: Could a closer look at Nimrod from above reveal more clues? 255 00:16:09,760 --> 00:16:12,400 - We can see several structures here that were clearly 256 00:16:12,560 --> 00:16:16,200 created to defend the city from attacking raiders. 257 00:16:16,360 --> 00:16:20,160 - And, Nimrod has a well documented history rife with conflict 258 00:16:20,320 --> 00:16:23,800 and destruction, underlining the reality that a city this rich, 259 00:16:23,960 --> 00:16:25,840 is a target for conquest. 260 00:16:26,000 --> 00:16:28,520 - Nimrod withstood a lot of attacks, 261 00:16:28,680 --> 00:16:31,520 a lot of raids over the centuries, but it was finally 262 00:16:31,680 --> 00:16:36,480 sacked for good when the Assyrian empire fell to a coalition that was 263 00:16:36,640 --> 00:16:41,680 led by Babylonia and Medea at the end of the seventh century BCE. 264 00:16:42,880 --> 00:16:46,480 - Is that what happened to these grand and wealthy Ksars of Djado? 265 00:16:48,240 --> 00:16:51,840 NARRATOR: Perhaps there's a clue almost 9000 km away, 266 00:16:52,000 --> 00:16:55,040 in the Gobi Desert of Western Inner Mongolia with another 267 00:16:55,200 --> 00:16:57,960 abandoned desert city, Khara-Khoto. 268 00:17:00,680 --> 00:17:05,760 - Founded in 1032 CE as the capital of the Western Xia Dynasty, 269 00:17:05,920 --> 00:17:08,000 this city was also a thriving trade centre, 270 00:17:09,160 --> 00:17:12,720 located on an important trade route through Asia. 271 00:17:12,880 --> 00:17:14,480 - But, just like Nimrod, 272 00:17:14,640 --> 00:17:18,400 the rich city caught the eye of unfriendly invaders. 273 00:17:18,560 --> 00:17:21,920 It was captured by Genghis Khan in 1226. 274 00:17:23,720 --> 00:17:26,960 - Khara-Khoto actually flourished under Mongol rule. 275 00:17:27,120 --> 00:17:30,680 During Kubla Kahn's time, the city expanded to 3 times its original 276 00:17:30,840 --> 00:17:35,400 size, and was even mentioned by Marco Polo in his travel logs. 277 00:17:35,560 --> 00:17:38,200 - Under the Mongols, the people were able to enjoy a peaceful 278 00:17:38,360 --> 00:17:40,960 existence for about 150 years, and that's 279 00:17:41,120 --> 00:17:47,120 until the Ming dynasty turned up in 1372 and laid siege to the city. 280 00:17:49,000 --> 00:17:52,640 - Now, no one knows exactly how Khara-Khoto fell, but the most 281 00:17:52,800 --> 00:17:55,720 commonly accepted theory is that the Ming rulers diverted the 282 00:17:55,880 --> 00:17:59,680 Ejin River, the city's only water source, that flowed just outside 283 00:17:59,840 --> 00:18:04,760 the fortress thus denying the city's troops and inhabitants water. 284 00:18:04,920 --> 00:18:07,920 - Is this what happened to Ksars of Djado? 285 00:18:08,080 --> 00:18:10,840 Did an outside enemy wipe out the people here? 286 00:18:11,920 --> 00:18:13,560 - It doesn't look like it. 287 00:18:13,720 --> 00:18:16,800 While the city was almost attacked in the 18th 288 00:18:16,960 --> 00:18:20,680 and 19th century by all these waves of nomadic raiders, it wasn't 289 00:18:20,840 --> 00:18:24,760 until the arrival of the French military in 1923 that the 290 00:18:24,920 --> 00:18:29,160 Ksars of Djado lost their independence. 291 00:18:29,320 --> 00:18:32,400 NARRATOR: If the people of the Ksars of Djado were not starved out 292 00:18:32,560 --> 00:18:38,160 or killed by a foreign power, why and how did they disappear? 293 00:18:38,320 --> 00:18:44,320 - How did this spectacular desert city end up becoming a ghost town? 294 00:18:46,200 --> 00:18:50,960 NARRATOR: An answer may be found just over 1600 km away in Mali, 295 00:18:51,120 --> 00:18:56,000 home of the legendary Saharan city, Timbuktu. 296 00:18:56,160 --> 00:18:59,680 - Once dubbed the 'city of gold' Timbuktu was a prosperous 297 00:18:59,840 --> 00:19:03,240 commercial hub for the ivory, salt and gold trades. 298 00:19:03,400 --> 00:19:06,600 It was also, a hub for the slave trade. 299 00:19:06,760 --> 00:19:10,640 NARRATOR: Timbuktu is still going today - but barely. 300 00:19:11,600 --> 00:19:16,400 - Timbuktu is struggling to survive and it's this modern struggle that 301 00:19:16,560 --> 00:19:21,880 holds a crucial clue to the downfall of the ancient Ksars of Djado. 302 00:19:23,440 --> 00:19:25,640 - It's being eaten up by the desert. 303 00:19:27,640 --> 00:19:30,600 - When it was built in the 5th century BCE, Timbuktu, 304 00:19:30,760 --> 00:19:34,560 like Djado, thrived in a lush liveable landscape. 305 00:19:34,720 --> 00:19:37,240 But now, the desert is moving in and the city is 306 00:19:37,400 --> 00:19:40,280 suffering from rapid desertification. 307 00:19:40,440 --> 00:19:43,880 - Desertification is an increasingly widespread problem as climate 308 00:19:44,040 --> 00:19:45,760 change modifies weather patterns, 309 00:19:45,920 --> 00:19:49,360 leaving people to deal with hyper arid conditions. 310 00:19:49,520 --> 00:19:52,200 - The Sahara Desert is no exception - scientists have observed 311 00:19:52,360 --> 00:19:56,480 that in the last century, the Saraha has expanded by 10 percent. 312 00:19:56,640 --> 00:20:00,200 And the problem is especially bad in Timbuktu - in Mali, 313 00:20:00,360 --> 00:20:06,400 the Sahara there is expanding at a rate of 48 km every year! 314 00:20:06,560 --> 00:20:10,800 - So could a similar thing have happened to Ksars of Djado? 315 00:20:12,160 --> 00:20:13,600 - It's possible. 316 00:20:13,760 --> 00:20:17,480 These ruins are 800 to 1000 years old - and that means that they 317 00:20:17,640 --> 00:20:21,120 were built at a time when this part of the Sahara was much wetter. 318 00:20:21,280 --> 00:20:25,400 NARRATOR: And just like Timbuktu, relentless desert swallowed Djado. 319 00:20:28,800 --> 00:20:31,360 - So it's very likely that what pushed people to abandon 320 00:20:31,520 --> 00:20:34,360 Djado was the lack of a clean water supply. 321 00:20:34,520 --> 00:20:37,320 You had this lush landscape, and then it all turned into desert, 322 00:20:37,480 --> 00:20:40,760 and that environment was just too harsh for humans. 323 00:20:42,560 --> 00:20:44,680 - Djado was then pretty much unlivable, 324 00:20:44,840 --> 00:20:47,920 and by the early 1900s, it was abandoned. 325 00:20:48,080 --> 00:20:51,440 - The people are long gone but the Ksars of Djado were 326 00:20:51,600 --> 00:20:55,200 so well constructed that the abandonment of the city did 327 00:20:55,360 --> 00:20:57,840 not mean it was destroyed. 328 00:20:59,280 --> 00:21:02,080 NARRATOR: Isolated from the outside world and built to last, 329 00:21:02,240 --> 00:21:05,520 the great Ksars of Djado stand tall today. 330 00:21:06,920 --> 00:21:09,960 A long-forgotten ghost city, its secrets 331 00:21:10,120 --> 00:21:13,400 uncovered by a view from above. 332 00:21:17,160 --> 00:21:20,760 On the densely forested slopes of the eastern Peruvian Andes, 333 00:21:20,920 --> 00:21:23,800 over 600 km north of Lima 334 00:21:23,960 --> 00:21:27,000 a view from above reveals an ancient wonder. 335 00:21:28,520 --> 00:21:31,640 Sitting high on the mountain ridge, 3000 meters 336 00:21:31,800 --> 00:21:36,520 above sea level, this mysterious stone site is known as Kuelap. 337 00:21:36,680 --> 00:21:38,280 - Look at that wall! 338 00:21:41,440 --> 00:21:44,800 NARRATOR: This epic structure surrounds all of Kuelap with a 339 00:21:44,960 --> 00:21:50,600 length of over 1000 meters - and, in some places stands 20 meters tall. 340 00:21:52,120 --> 00:21:54,200 - It's constructed from limestone blocks - 341 00:21:54,360 --> 00:21:58,320 some with an estimated weight of 3 tons - that's as heavy as a hippo! 342 00:22:00,960 --> 00:22:04,280 - That wall is on the scale of a fortress - is this structure 343 00:22:04,440 --> 00:22:09,040 an abandoned military base or the site of an old castle? 344 00:22:09,200 --> 00:22:13,040 NARRATOR: Is Kuelap the ruins of a fortified city? 345 00:22:13,200 --> 00:22:17,480 - Even though it may look, uh, as a defensive construction, 346 00:22:17,640 --> 00:22:21,520 we have to take into consideration that there is no parapet. 347 00:22:22,480 --> 00:22:25,480 - Okay so if there's no parapet like you'd usually 348 00:22:25,640 --> 00:22:28,600 see around a fortress - what about that huge, long wall - 349 00:22:28,760 --> 00:22:31,760 isn't that also a classic fortress feature? 350 00:22:31,920 --> 00:22:36,880 - In some parts, the surrounding wall is 20 meters high. 351 00:22:37,040 --> 00:22:38,760 In other parts it's only six. 352 00:22:39,600 --> 00:22:42,680 NARRATOR: Some parts of the wall are far too low to provide any 353 00:22:42,840 --> 00:22:46,800 protection - and there's something else missing at Kuelap, 354 00:22:46,960 --> 00:22:48,840 something crucial to survival. 355 00:22:49,000 --> 00:22:51,920 - There's no water inside. 356 00:22:52,080 --> 00:22:54,880 Water has to be brought from the springs that we 357 00:22:55,040 --> 00:22:57,920 have around Kuelap or from the river. 358 00:22:58,080 --> 00:23:03,200 So knowing that there is no water reservoirs, no springs inside, 359 00:23:03,360 --> 00:23:08,880 we can completely disregard the idea that Kuelap was a fortress. 360 00:23:09,040 --> 00:23:11,560 NARRATOR: So what is this place? 361 00:23:11,720 --> 00:23:14,960 A view from above reveals a network of strange stone 362 00:23:15,120 --> 00:23:20,200 circles across Kuelap. Could these mysterious rings provide any clues? 363 00:23:21,040 --> 00:23:23,600 - Did they hold water - is this like an ancient spa? 364 00:23:23,760 --> 00:23:25,760 Or were they food storage structures, 365 00:23:25,920 --> 00:23:28,640 like modern day farm silos? 366 00:23:28,800 --> 00:23:32,000 - Those stone circles are really intriguing- 367 00:23:32,160 --> 00:23:35,360 maybe they have some sort of ritual purpose? 368 00:23:35,520 --> 00:23:37,320 NARRATOR: Perhaps clues can be uncovered 369 00:23:37,480 --> 00:23:41,080 halfway across the world at Mycenae in Greece, 370 00:23:41,240 --> 00:23:43,320 where a view from above reveals another set 371 00:23:43,480 --> 00:23:45,520 of mysterious stone circles. 372 00:23:48,120 --> 00:23:51,320 Excavations at Mycenae revealed that these large stone 373 00:23:51,480 --> 00:23:53,960 circles are grave sites. 374 00:23:54,120 --> 00:23:57,520 - Those circles contained skeletons from the royal families - 375 00:23:57,680 --> 00:24:01,920 accompanied by a treasure trove of their personal stuff. 376 00:24:02,080 --> 00:24:05,480 - So could the strange stone circles at Kuelap have been 377 00:24:05,640 --> 00:24:08,800 part of a burial site like we see at Mycenae? 378 00:24:08,960 --> 00:24:10,760 Could they be tombs? 379 00:24:10,920 --> 00:24:13,960 NARRATOR: Investigations at Kuelap have uncovered a clue, 380 00:24:14,120 --> 00:24:16,600 human remains. 381 00:24:16,760 --> 00:24:23,240 - That is definitely related to the importance to venerate 382 00:24:23,400 --> 00:24:28,280 our grandfathers and great-grandfathers even after 383 00:24:28,440 --> 00:24:31,320 they have died a long time ago. 384 00:24:32,600 --> 00:24:35,360 - So if human bones were found in these circles, 385 00:24:35,520 --> 00:24:38,400 these must be the remains of tombs. 386 00:24:38,560 --> 00:24:41,000 NARRATOR: But a closer look at these circles reveals something 387 00:24:41,160 --> 00:24:42,840 unexpected. 388 00:24:45,000 --> 00:24:49,680 - There's evidence of some kind of wooden structure where 389 00:24:49,840 --> 00:24:52,520 they could put the bed where they slept 390 00:24:52,680 --> 00:24:56,480 and also where they can store other goods. 391 00:24:56,640 --> 00:25:01,480 Then we have the kitchen area where the fire is located. 392 00:25:01,640 --> 00:25:05,440 - It's basically a multi-familiar building that is a circular 393 00:25:05,600 --> 00:25:10,240 construction that has a diameter that can vary between five 394 00:25:10,400 --> 00:25:11,960 and 10 meters. 395 00:25:12,120 --> 00:25:16,960 There's some characteristics that are always inside these huts. 396 00:25:17,120 --> 00:25:21,360 The tomb where they kept some bones of their ancestors is usually 397 00:25:21,520 --> 00:25:23,680 located in the centre of the building. 398 00:25:24,920 --> 00:25:28,880 NARRATOR: There are more than 400 of these multi-family houses in Kuelap. 399 00:25:30,080 --> 00:25:34,640 - If we make the math with the amount of people that can 400 00:25:34,800 --> 00:25:39,560 live in one of these huts, we are talking about at its height, 401 00:25:39,720 --> 00:25:46,160 a population of around 2,500 people living in Kuelap. 402 00:25:47,200 --> 00:25:50,840 - So if those circles were once houses to a lot of people, 403 00:25:51,000 --> 00:25:52,800 who were they? 404 00:25:52,960 --> 00:25:55,680 NARRATOR: A wider view from above reveals another clue, 405 00:25:55,840 --> 00:25:58,520 a dramatic rectangular structure. 406 00:25:58,680 --> 00:26:04,520 - This one is the biggest building in Kuelap. It's called a Kallanka. 407 00:26:04,680 --> 00:26:09,360 It's a symbol of power of the Incas. 408 00:26:09,520 --> 00:26:12,040 - Finding the ruins of Kallanka is like finding a giant sign 409 00:26:12,200 --> 00:26:13,880 that says, 'The Inca were here'. 410 00:26:14,040 --> 00:26:16,560 It's an unambiguous stamp that this place was definitely 411 00:26:16,720 --> 00:26:19,000 part of the Inca Empire. 412 00:26:19,160 --> 00:26:22,520 NARRATOR: So did the Inca build Kuelap? 413 00:26:22,680 --> 00:26:25,640 - Kuelap isn't very far from the world-famous Machu Picchu 414 00:26:25,800 --> 00:26:29,360 which was built by the Inca - is this another one of their creations? 415 00:26:30,720 --> 00:26:34,480 - According to the radiocarbon dating's that we have, 416 00:26:34,640 --> 00:26:38,160 Kuelap was built around 600 AD. 417 00:26:39,120 --> 00:26:42,520 - Machu Picchu is dated to almost a 1000 years later than that - 418 00:26:42,680 --> 00:26:46,000 so Kuelap was built long before the Inca started up. 419 00:26:46,160 --> 00:26:49,880 NARRATOR: But if the Inca aren't behind this ancient site, who is? 420 00:26:51,680 --> 00:26:54,160 - Kuelap and all the settlements around were 421 00:26:54,320 --> 00:26:56,360 built by the Chachapoya culture. 422 00:26:56,520 --> 00:27:01,800 Chachapoya is a generic name that the Incas started 423 00:27:01,960 --> 00:27:05,480 using for the people that live in this huge 424 00:27:05,640 --> 00:27:08,160 area of approximately 200,000 square kilometres. 425 00:27:11,560 --> 00:27:13,960 - There's a lot of mystery surrounding these people 426 00:27:14,120 --> 00:27:15,520 and their culture. 427 00:27:15,680 --> 00:27:20,000 - We know they thrived in a region of Northern Peru from about 900 428 00:27:20,160 --> 00:27:25,280 to 1400 CE, but they didn't have a written language, so much 429 00:27:25,440 --> 00:27:30,240 of what we know of them comes from studying the ruins they left behind. 430 00:27:30,400 --> 00:27:33,480 - But, wait, if the Chachapoya built Kuelap, 431 00:27:33,640 --> 00:27:35,960 then what's with all the Inca stuff here? 432 00:27:37,520 --> 00:27:42,240 NARRATOR: From 1438 to 1533 the Incan Empire grew rapidly - 433 00:27:42,400 --> 00:27:45,360 becoming the largest empire ever seen in the Americas. 434 00:27:47,200 --> 00:27:50,920 As they expanded north through Peru, the Inca conquered Kuelap 435 00:27:51,080 --> 00:27:53,600 and ruled over the Chachapoya people. 436 00:27:53,760 --> 00:27:59,240 But around the mid 16th century, Kuelap was suddenly abandoned. 437 00:27:59,400 --> 00:28:01,320 - Why would the mighty Inca Empire go to all 438 00:28:01,480 --> 00:28:03,120 the trouble of conquering this place, 439 00:28:03,280 --> 00:28:07,520 putting up all these buildings and then just abandon Kuelap? 440 00:28:10,600 --> 00:28:14,080 NARRATOR: Perhaps there's a clue more than 12,000 kilometres 441 00:28:14,240 --> 00:28:19,880 away near the Sea of Galilee, with another abandoned city - Gamla. 442 00:28:20,040 --> 00:28:24,360 - Gamla has plenty in common with Kuelap - a defensive stone wall, 443 00:28:24,520 --> 00:28:29,480 residential housing and dedicated space for rituals and celebration. 444 00:28:29,640 --> 00:28:34,320 NARRATOR: Like Kuelap, Gamla was a thriving city but in the 1st 445 00:28:34,480 --> 00:28:38,480 century Roman soldiers attacked, leaving destruction in their wake. 446 00:28:40,960 --> 00:28:43,560 - Was Kuelap abandoned because it was invaded? 447 00:28:43,720 --> 00:28:47,480 - Is this what led to Kuelap's abandonment? 448 00:28:47,640 --> 00:28:49,120 - That's exactly what happened here. 449 00:28:49,280 --> 00:28:52,240 In the mid-1500's, the Spanish conquered the area 450 00:28:52,400 --> 00:28:57,200 and ended the Inca's 70-year reign in Kuelap. 451 00:28:57,360 --> 00:29:00,400 NARRATOR: The conquered Inca and Chachapoya were rounded up 452 00:29:00,560 --> 00:29:02,640 and Kuelap was abandoned. 453 00:29:02,800 --> 00:29:05,880 Since then - Kuelap has stood frozen in time, 454 00:29:06,040 --> 00:29:09,040 an ancient testament to a once mighty city. 455 00:29:09,200 --> 00:29:13,120 But now - the view from above reveals Kuelap has a more 456 00:29:13,280 --> 00:29:15,040 modern mystery to be solved. 457 00:29:15,200 --> 00:29:18,000 - One of the mysteries of La Fortaleza de Kuelap is 458 00:29:18,160 --> 00:29:22,560 the collapse of the southern perimeter wall in 2022. 459 00:29:22,720 --> 00:29:24,840 NARRATOR: A huge stretch of this giant wall, 460 00:29:25,000 --> 00:29:28,320 almost 30 metres long - simply gave out. 461 00:29:29,680 --> 00:29:33,080 - People immediately began to ask if this monument is a thousand 462 00:29:33,240 --> 00:29:38,040 years old and has withstood time, why is it falling down now? 463 00:29:38,200 --> 00:29:40,920 NARRATOR: What modern phenomena could be causing this 464 00:29:41,080 --> 00:29:42,920 kind of damage to the wall? 465 00:29:43,080 --> 00:29:47,160 - Is Kuelap a victim of natural forces? 466 00:29:47,320 --> 00:29:49,920 NARRATOR: Peru is located in the Ring of Fire - 467 00:29:50,080 --> 00:29:54,560 where more than 80% of the world's largest earthquakes occur. 468 00:29:54,720 --> 00:29:57,160 - The ring of fire is this giant belt that wraps around the 469 00:29:57,320 --> 00:30:00,520 Pacific ocean where lots of our planet's tectonic plates meet. 470 00:30:00,680 --> 00:30:02,320 When they slip beneath each other, 471 00:30:02,480 --> 00:30:04,720 that's when you get all kinds of earthquakes. 472 00:30:06,040 --> 00:30:09,840 NARRATOR: Two earthquakes did hit the region in 2022 - 473 00:30:10,000 --> 00:30:13,800 but neither were strong enough to cause this level of destruction. 474 00:30:13,960 --> 00:30:17,480 - So we can cross earthquake damage off the list. 475 00:30:17,640 --> 00:30:21,160 Why else would the wall at Kuelap come down so quickly - 476 00:30:21,320 --> 00:30:26,160 especially after standing strong for centuries? 477 00:30:26,320 --> 00:30:28,720 NARRATOR: Perhaps, the collapse of the wall was caused 478 00:30:28,880 --> 00:30:34,320 not by outside forces, but instead, forces within. 479 00:30:34,480 --> 00:30:36,320 - We have elements here, 480 00:30:36,480 --> 00:30:40,680 some clues to solve the mystery of the history of the collapses here. 481 00:30:40,840 --> 00:30:44,600 Water has accumulated behind this wall, 482 00:30:44,760 --> 00:30:49,640 it's been turned a little bit into a dam, and this interior core 483 00:30:49,800 --> 00:30:54,400 made of mud and stone, has gone from solid to be a little more plastic. 484 00:30:54,560 --> 00:30:59,560 And it's sitting on a sloping terrain. So it begins pushing down. 485 00:30:59,720 --> 00:31:02,400 And the perimeter wall, however solid 486 00:31:02,560 --> 00:31:07,040 and massive it is, cannot hold the weight of this plastic core. 487 00:31:07,200 --> 00:31:09,240 And this is how the collapse has happened. 488 00:31:11,000 --> 00:31:12,880 We have solved one mystery. 489 00:31:13,040 --> 00:31:16,600 Now we have confirmed that water infiltration is the ultimate 490 00:31:16,760 --> 00:31:19,680 cause of the collapse of the perimeter walls. 491 00:31:19,840 --> 00:31:24,720 But obviously, another mystery remains. Why now? 492 00:31:24,880 --> 00:31:26,840 - What could possibly cause this wall, 493 00:31:27,000 --> 00:31:30,520 that's stood strong for about a 1000 years, to just start crumbling? 494 00:31:31,680 --> 00:31:34,080 NARRATOR: Scientists believe the cause of this problem 495 00:31:34,240 --> 00:31:35,880 comes from above. 496 00:31:40,840 --> 00:31:43,920 - Because of the great amount of precipitation in this area, 497 00:31:44,080 --> 00:31:49,640 one of the main theories is the infiltration of rainwater. 498 00:31:49,800 --> 00:31:52,400 - Rain? That is the culprit? 499 00:31:52,560 --> 00:31:56,440 I can see how an earthquake might cause damage like this, but rain! 500 00:31:56,600 --> 00:31:59,560 Is it really that powerful? 501 00:31:59,720 --> 00:32:01,880 - The rainy season here is very heavy, 502 00:32:02,040 --> 00:32:05,160 perhaps up to 3000 millimetres a year. 503 00:32:06,960 --> 00:32:09,760 NARRATOR: But why now, after 1000 years, 504 00:32:09,920 --> 00:32:13,280 is rain such a threat to the wall - and all of Kuelap? 505 00:32:15,000 --> 00:32:18,120 - So, we use data from some weather stations 506 00:32:18,280 --> 00:32:23,360 and mostly satellites to reconstruct the patterns of precipitation 507 00:32:23,520 --> 00:32:25,400 for the last four decades. 508 00:32:25,560 --> 00:32:28,240 And that was a real discovery. 509 00:32:28,400 --> 00:32:31,320 The precipitation has been growing over time, 510 00:32:31,480 --> 00:32:36,400 it's about 4% higher today than it was in the 1980s. 511 00:32:36,560 --> 00:32:39,920 And out of seven historically high precipitation 512 00:32:40,080 --> 00:32:45,000 months in those 40 years, four occurred in the last five years. 513 00:32:45,160 --> 00:32:47,760 So there is an increasing trend, 514 00:32:47,920 --> 00:32:50,920 and that is becoming more critical in the last few years. 515 00:32:53,800 --> 00:32:56,160 NARRATOR: One year after the collapse of the wall, 516 00:32:56,320 --> 00:33:00,640 Peru is experiencing what's called a Coastal El Nino, a weather 517 00:33:00,800 --> 00:33:05,360 event that's expected to bring more torrential rain to the area. 518 00:33:05,520 --> 00:33:08,200 - The amount of water that it's receiving today, 519 00:33:08,360 --> 00:33:12,400 due to climate change, may be exceeding its capabilities. 520 00:33:13,760 --> 00:33:16,440 NARRATOR: Recent satellite imagery has revealed that the surface 521 00:33:16,600 --> 00:33:20,800 water off the coast of Peru is about 6 degrees higher than normal. 522 00:33:22,320 --> 00:33:25,160 - When you've got warm water like this, it adds heat to the air, 523 00:33:25,320 --> 00:33:29,520 which means it can hold more water, which means bigger rainfall. 524 00:33:29,680 --> 00:33:33,000 - And bigger rainfall means more water is 525 00:33:33,160 --> 00:33:35,600 getting into the core of Kuelap's wall. 526 00:33:35,760 --> 00:33:37,880 - If we don't mitigate the infiltration, 527 00:33:38,040 --> 00:33:41,440 the core is going to become plastic and push the perimeter walls 528 00:33:41,600 --> 00:33:44,880 out, and the whole monument is going to collapse. 529 00:33:47,560 --> 00:33:50,120 - It's a race against the clock - can you figure out 530 00:33:50,280 --> 00:33:54,080 how to protect the site before the next round of catastrophic rain. 531 00:33:55,120 --> 00:33:59,040 - It would be such a tragedy if the site of Kuelap washed away - 532 00:33:59,200 --> 00:34:02,920 there is so much history and still so much to be discovered there. 533 00:34:04,280 --> 00:34:07,240 NARRATOR: Scientists are determined to preserve this magnificent 534 00:34:07,400 --> 00:34:11,640 city - and thanks to their research, they now know what needs to be done. 535 00:34:13,360 --> 00:34:15,880 - We should be mitigating the infiltration. 536 00:34:16,040 --> 00:34:17,840 And when that has stabilized, 537 00:34:18,000 --> 00:34:20,280 then we can reconstruct the perimeter walls. 538 00:34:20,440 --> 00:34:22,840 With the goal of preserving this for future generations, 539 00:34:23,000 --> 00:34:24,560 for everyone to enjoy. 540 00:34:25,680 --> 00:34:28,160 NARRATOR: A mystery solved - and a discovery that could 541 00:34:28,320 --> 00:34:32,320 help save an ancient city all with a view from above. 542 00:34:37,000 --> 00:34:40,080 High over the arid plains of Northern China, in the remote 543 00:34:40,240 --> 00:34:45,200 desert of Inner Mongolia a view from above reveals something unexpected. 544 00:34:50,480 --> 00:34:53,360 - It looks utterly abandoned - what happened here? 545 00:34:54,520 --> 00:34:58,280 - It's totally empty! Where did everyone go? 546 00:34:58,440 --> 00:35:01,760 - It totally looks like something out of a science fiction movie! 547 00:35:01,920 --> 00:35:05,280 NARRATOR: The official name of the city is 'Kangbashi New Town' 548 00:35:05,440 --> 00:35:10,000 but it's often referred to by the area in which it's built - Ordos. 549 00:35:11,320 --> 00:35:14,440 The story of Ordos begins in the early 2000's 550 00:35:14,600 --> 00:35:16,280 when the Chinese government began to build 551 00:35:16,440 --> 00:35:21,120 the city in the Ordos Desert, spending one billion dollars. 552 00:35:21,280 --> 00:35:24,840 - Ordos was designed to provide everything a modern city 553 00:35:25,000 --> 00:35:27,040 could possibly need or desire, 554 00:35:27,200 --> 00:35:31,080 all for a population of at least a million people. 555 00:35:31,240 --> 00:35:35,600 - So where are they? Where are all the people? 556 00:35:35,760 --> 00:35:39,920 - It looks apocalyptic - like, something just wiped everyone out! 557 00:35:40,080 --> 00:35:44,240 - Was this city emptied by a sudden, massive disaster? 558 00:35:44,400 --> 00:35:47,920 NARRATOR: Perhaps a clue can be found more than 6000 km 559 00:35:48,080 --> 00:35:53,000 away in Ukraine, home to one of the biggest disasters in modern times. 560 00:35:54,720 --> 00:35:59,360 - On April 25 and 26, 1986, a faulty Soviet 561 00:35:59,520 --> 00:36:03,960 reactor at the Chernobyl nuclear power plant exploded. 562 00:36:06,280 --> 00:36:08,320 NARRATOR: As the radiation spread through the air, 563 00:36:08,480 --> 00:36:10,560 it covered more than 40% of Europe. 564 00:36:12,760 --> 00:36:15,840 - Today, almost forty years later, there is still a 30 kilometre 565 00:36:16,960 --> 00:36:20,360 'exclusion zone' around the plant - scientists estimate this 566 00:36:20,520 --> 00:36:24,720 zone around Chernobyl will not be habitable for up to 20,000 years. 567 00:36:27,320 --> 00:36:31,400 - It looks eerily similar to Ordos all these empty buildings, 568 00:36:31,560 --> 00:36:34,680 sort of frozen in time and empty. 569 00:36:34,840 --> 00:36:38,400 - Did a similar disaster happen to Ordos? 570 00:36:39,960 --> 00:36:42,280 - No records exist that Ordos suffered 571 00:36:42,440 --> 00:36:45,720 anything like Chernobyl - the city isn't a designated danger zone 572 00:36:45,880 --> 00:36:48,920 and is actually perfectly safe to live in. 573 00:36:49,080 --> 00:36:51,560 - In fact, the region is quite prosperous. 574 00:36:51,720 --> 00:36:53,720 I mean yes, it's essentially a desert, 575 00:36:53,880 --> 00:36:58,320 but the landscape is rich in resources - particularly, coal. 576 00:36:58,480 --> 00:37:00,760 - And that's why Ordos was built here. 577 00:37:00,920 --> 00:37:03,480 A coal boom in the early 2000's compelled the local 578 00:37:03,640 --> 00:37:06,320 government to splurge on this new development. 579 00:37:06,480 --> 00:37:10,320 - So, if Ordos is considered a completely safe place to live 580 00:37:10,480 --> 00:37:16,280 and it was supported by a rich industry, why is it empty? 581 00:37:16,440 --> 00:37:20,280 NARRATOR: There may be a clue far to the southwest in Namibia, 582 00:37:20,440 --> 00:37:22,840 in another abandoned desert city. 583 00:37:25,160 --> 00:37:28,360 - Once a prosperous diamond mining town, Kolmanskop was abandoned 584 00:37:28,520 --> 00:37:32,320 when the diamonds ran out and better resources were found elsewhere. 585 00:37:32,480 --> 00:37:35,560 - And ever since, the fast-moving Namibian Desert has been 586 00:37:35,720 --> 00:37:39,400 closing in and literally, swallowing up the town. 587 00:37:39,560 --> 00:37:42,320 - Satellite observations found that the average rate at which 588 00:37:42,480 --> 00:37:47,560 the dunes in this area moved ranged from 7 to 32 meters per year! 589 00:37:47,720 --> 00:37:50,400 - The Kolmanskop is not alone. 590 00:37:50,560 --> 00:37:54,760 The Namibian desert has been swallowing more than just the towns. 591 00:37:54,920 --> 00:37:57,760 NARRATOR: One of the most famous examples of the desert's power to 592 00:37:57,920 --> 00:38:01,080 consume, can be found over 400 kilometres away, 593 00:38:01,240 --> 00:38:03,360 on Namibia's Skeleton Coast. 594 00:38:06,680 --> 00:38:10,520 - The waters off this place are famous for their strong currents, 595 00:38:10,680 --> 00:38:15,640 dense fogs, and treacherous sand banks that constantly move. 596 00:38:15,800 --> 00:38:17,960 These extreme climatic conditions 597 00:38:18,120 --> 00:38:21,480 when combined with strong sandstorms have been considered 598 00:38:21,640 --> 00:38:26,080 the cause of the sinking of over a thousand ships. 599 00:38:26,240 --> 00:38:29,680 NARRATOR: The eerie remnants of long-lost ships and stranded 600 00:38:29,840 --> 00:38:33,360 sea creatures lies scattered across this desolate landscape. 601 00:38:35,080 --> 00:38:37,960 - Is something like this happening to Ordos? 602 00:38:38,120 --> 00:38:41,400 - Is Ordos being buried by sand? 603 00:38:41,560 --> 00:38:44,400 NARRATOR: A view from above shows that Ordos is on the edge 604 00:38:44,560 --> 00:38:50,880 of the Gobi Desert - the fastest growing desert in the world. 605 00:38:51,040 --> 00:38:53,560 - Between 1975 and 2017, 606 00:38:53,720 --> 00:38:59,720 China's deserts expanded by an astonishing 21,000 square miles. 607 00:39:01,320 --> 00:39:05,360 - That's equivalent to more than 10 million football fields! 608 00:39:05,520 --> 00:39:08,120 - The catalyst for this is deforestation. 609 00:39:08,280 --> 00:39:11,880 All the upheaval and removal of huge, ancient roots means the 610 00:39:12,040 --> 00:39:17,240 soil isn't held together and is more vulnerable to natural wind erosion. 611 00:39:17,400 --> 00:39:20,360 - China has tried planting trees to hold back the desert with a 'Green 612 00:39:20,520 --> 00:39:24,920 Great Wall' but a fifth of the trees planted so far have been planted 613 00:39:25,080 --> 00:39:29,480 in places they don't naturally grow, so they've already died. 614 00:39:30,480 --> 00:39:34,760 - So is the fast-approaching desert what forced people to flee the city? 615 00:39:36,160 --> 00:39:39,280 NARRATOR: But a view from above reveals massive reservoirs 616 00:39:39,440 --> 00:39:41,880 supplying Ordos City. 617 00:39:42,040 --> 00:39:44,960 - So while there's no question the desert is expanding, 618 00:39:45,120 --> 00:39:48,680 between the solid, modern buildings and the giant reservoirs, 619 00:39:48,840 --> 00:39:51,560 it's unlikely that people would think the approaching desert 620 00:39:51,720 --> 00:39:52,920 was a problem. 621 00:39:53,080 --> 00:39:54,760 NARRATOR: So if people didn't flee 622 00:39:54,920 --> 00:39:59,240 because they feared being swallowed up by the desert then why? 623 00:39:59,400 --> 00:40:04,240 What turned the massive city of Ordos into a ghost town? 624 00:40:05,760 --> 00:40:07,840 - It doesn't appear that the city was abandoned 625 00:40:08,000 --> 00:40:12,320 because of some kind of disaster - man-made or natural. 626 00:40:12,480 --> 00:40:14,680 - So where is everybody? 627 00:40:14,840 --> 00:40:18,200 NARRATOR: Perhaps an answer to this mystery lies more than 1000 km 628 00:40:18,360 --> 00:40:21,280 away, in another strange city in China. 629 00:40:26,520 --> 00:40:29,160 - Oh that is bizarre! I mean just look at that! 630 00:40:29,320 --> 00:40:32,520 I mean it's a total replica of an English town - 631 00:40:32,680 --> 00:40:36,560 complete with pubs and old-time English architecture. 632 00:40:36,720 --> 00:40:40,560 - This just gets weirder and weirder. 633 00:40:40,720 --> 00:40:42,560 NARRATOR: This is Thames Town. 634 00:40:42,720 --> 00:40:46,400 Created in 2006, the town was meant to be home for the thousands 635 00:40:46,560 --> 00:40:51,080 of people who live and work at nearby universities. 636 00:40:51,240 --> 00:40:56,920 - The city was expensive to build - an estimated 635 million dollars. 637 00:40:57,080 --> 00:41:00,480 And, expensive to live in. Too much so, in fact. 638 00:41:00,640 --> 00:41:04,240 - Thames Town was almost as expensive to live in as London 639 00:41:04,400 --> 00:41:07,880 itself, now that is saying something! 640 00:41:08,040 --> 00:41:09,640 - It's bonkers. Really! 641 00:41:09,800 --> 00:41:12,160 I mean, how much money did they think people who live 642 00:41:12,320 --> 00:41:14,720 and work at Universities make?! - In the end, 643 00:41:14,880 --> 00:41:19,000 the government only managed to get a few thousand people to live there. 644 00:41:19,160 --> 00:41:22,280 NARRATOR: And Thamestown is not the only time this happened - 645 00:41:22,440 --> 00:41:25,360 another city built to look like Paris, France, 646 00:41:25,520 --> 00:41:29,480 also failed because no one could afford to live there. 647 00:41:29,640 --> 00:41:32,160 - So, is this what happened to Ordos? 648 00:41:32,320 --> 00:41:34,760 Is this massive city virtually empty 649 00:41:34,920 --> 00:41:38,480 because no one has enough money to survive there? 650 00:41:38,640 --> 00:41:41,040 - I think we're getting warmer. 651 00:41:41,200 --> 00:41:45,000 It cost well over a billion dollars to build Ordos. 652 00:41:45,160 --> 00:41:48,880 That meant developers needed high real estate prices to get 653 00:41:49,040 --> 00:41:50,920 a return on their investment. 654 00:41:51,080 --> 00:41:54,360 - But, people didn't sign up in droves the way the builders 655 00:41:54,520 --> 00:41:55,880 thought they would. 656 00:41:56,040 --> 00:41:58,760 - So, the developers were forced to scale back plans for a population 657 00:41:58,920 --> 00:42:03,640 of 1 million people but the actual population only reached 100,000. 658 00:42:03,800 --> 00:42:06,960 - And so you have what, 100,000 people being asked to make 659 00:42:07,120 --> 00:42:10,480 up the shortfall so developers could recoup their losses? 660 00:42:10,640 --> 00:42:12,280 Not a great plan - 661 00:42:12,440 --> 00:42:15,800 This drove the prices of everything through the roof. 662 00:42:15,960 --> 00:42:18,480 NARRATOR: And it got worse - at one point, 663 00:42:18,640 --> 00:42:22,680 property prices plunged so badly that many developers went bankrupt. 664 00:42:24,520 --> 00:42:28,680 - The Ordos project essentially fell flat on its face. 665 00:42:28,840 --> 00:42:31,680 They just couldn't get enough people living there to sustain it. 666 00:42:33,680 --> 00:42:35,280 - Looking over the city, 667 00:42:35,440 --> 00:42:39,440 it's easy to see why the unfinished houses and the vast, empty, 668 00:42:39,600 --> 00:42:44,480 dusty blocks of a city with insanely expensive real estate and 669 00:42:44,640 --> 00:42:50,480 impossible cost of living, didn't exactly attract droves of families. 670 00:42:50,640 --> 00:42:53,760 - The one thing that did make a difference was education. 671 00:42:53,920 --> 00:42:57,160 Over the past several years China has worked hard to make Ordos 672 00:42:57,320 --> 00:42:58,320 more attractive. 673 00:42:58,480 --> 00:43:02,000 The most successful of these efforts was bringing in good schools. 674 00:43:02,160 --> 00:43:05,400 - Education is highly valued in China and the promise 675 00:43:05,560 --> 00:43:10,640 of access to good schools has started to lure families to Ordos. 676 00:43:10,800 --> 00:43:14,120 - Slowly, the city is coming back but it is still 677 00:43:14,280 --> 00:43:18,760 nowhere near the epic metropolis it was designed to be. 678 00:43:18,920 --> 00:43:24,320 - Ordos is the ultimate lesson in arrogance and greed in the desert. 679 00:43:24,480 --> 00:43:29,200 NARRATOR: An epic urban folly, revealed only by a view from above. 680 00:43:33,040 --> 00:43:36,800 From a modern metropolis dangerously close to the edge, 681 00:43:36,960 --> 00:43:41,360 to an ancient walled city in the clouds, to a mysterious desert 682 00:43:41,520 --> 00:43:46,880 city losing the battle with nature and an abandoned urban disaster. 683 00:43:47,040 --> 00:43:49,320 Mysteries of these great cities clearly 684 00:43:49,480 --> 00:43:53,320 uncovered with a view from above. 685 00:43:56,360 --> 00:44:00,080 Subtitles by Sky Access Services 62714

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