Original subtitles

NARRATOR: They're watching you.

More than 5,000 satellites circle the Earth.

Every day, they uncover new, mysterious phenomena

that defy explanation.

Witches, kings, and mega weapons

in a 1,000-year-old forest.

Strange symbols have been found here.

What is this?

NARRATOR: Decoding the great plagues of Egypt.

It all happened just a few miles

from where this image is located.

NARRATOR: And the super warriors of Voodoo Lake.

It was referred to as the Sparta of Africa,

because this was a society of brutal warriors.

NARRATOR: Baffling phenomena, mysteries from space.

What on Earth are they?

[theme music playing]

NARRATOR: The New Forest, South Central England,

a vast expanse of woodland and wild gorse,

barely changed since the Norman conquest of England

in 1066.

People haven't been allowed to build here,

by royal decree, for over 1,000 years.

NARRATOR: Yet on June 5th, 2010,

an aerial LIDAR scanner reveals remnants

of a seemingly man-made structure buried

in a barren valley.

The image is really bizarre.

It's multiple concentric circles made up of

a series of smaller circles, really reminiscent

of a dartboard.

How long has this pattern been there?

How many ages has it been laying,

waiting to be discovered?

NARRATOR: Hooked by the weird circles,

archaeologist Rebecca Bradshaw is

trekking into the remote forest, which is anything

but new.

BRADSHAW: The forest has this extraordinary history.

It's a really ancient, spiritual space.

NARRATOR: In 1079, King William The Conqueror claims

this region as a royal hunting ground.

Peasants are driven out, threatened with death if

they disobey.

But death finds William.

Two of the king's sons meet their end here,

one slain by a hunter's arrow, the other in a riding accident.

The locals said that this was God's will

punishing him, because he removed

13 churches and scattered all the inhabitants,

making New Forest almost barren of people.

NARRATOR: But some return and make their mark on the woods,

leaving clues Bradshaw thinks could shed

light on the LIDAR image.

Strange symbols carved into trees and things

have been found here

and have confused a number of historians looking to document

the history of the New Forest.

NARRATOR: In the 18th and 19th centuries,

trees suitable for shipbuilding are

carved with the king's mark,

a broad arrow.

But there are also older carvings,

strange shapes, some of them reminiscent of the LIDAR image,

the work of medieval misfits,

spiritual outcasts who come to convene with the ancient forest.

On some of these trees,

they found concentric circles that

historians identify as witches' marks.

A square has corners and edges, whereas a circle doesn't,

and so it's a way of capturing evil,

circumscribing evil into one particular place.

NARRATOR: Evidence of witches' marks

can be traced to the early 1300s.

They are found in caves and medieval buildings

across Britain,

scored in the wooden beams of churches and domestic dwellings.

HYMEL: Witches would also carve them into the ground,

from where they would then conduct their spells.

HORTON: It is possible that these concentric circles

we see in the LIDAR image

is an example of these protection marks that you find

on trees and on buildings.

NARRATOR: But if these have been left by witches,

they are massive.

The largest is almost a mile wide.

They are of a size, scale, and precision

that really suggests a much more modern effort.

NARRATOR: Closing in on the site scanned from the skies...

What is this?

...Bradshaw finds further evidence that the strange

circles may be much more recent in origin.

On first glance, this, to me,

looks like extremely heavy duty concrete,

and the shape, of course, suggests...

[sniffles]

a bunker.

This is a bit odd, because it hasn't got

any visible

signs of where guns could go.

What is a non-defensive bunker doing here

in the middle of a pretty dense wooded area?

NARRATOR: Climbing out of the trees,

Bradshaw reaches a vantage point high above the valley

in the LIDAR image...

Well, well, well.

...where she finds a bizarre clue

that literally points the way.

This

looks to me

like 100 feet in length by sort of 30

to 40 feet wide, and it is pointing directly

into this valley here.

This is crazy.

NARRATOR: Up close, the giant arrow

serves no apparent purpose.

But Bradshaw considers a fresh perspective.

If you're a pilot coming through the skies,

you have indicators on the ground like this arrow to

direct you where you're going,

then it would make sense that those concentric circles

are actually a massive target.

NARRATOR: A mild descent into the valley...

Wow!

...and Bradshaw's theory hits the bull's eye.

This is a bomb crater.

I get the feeling that this is a Second World War

bombing range.

NARRATOR: But this is no ordinary bombing range.

The archaeologist estimates the width

of the crater at 100 feet plus.

It could easily be over 50 feet deep.

Something really quite extraordinary

was dropped here to make this size crater.

NARRATOR: Bradshaw has found evidence of

a cataclysmic experiment that rocked rural England.

What the British army did in the New Forest

was secret then, and had remained secret

for decades afterward.

Coming up, the mega blast that changed history.

The Germans didn't know what hit them.

NARRATOR: And blood of the mummies.

KOUROUNIS: It looks like some gigantic footprint

has just smashed into the desert.

NARRATOR: Archaeologist Rebecca Bradshaw

is in England's ancient New Forest...

This is a Second World War bombing range.

...investigating strange circles revealed by LIDAR.

BRADSHAW: Something really quite extraordinary

was dropped here to make this size crater.

NARRATOR: During World War II,

U.S. and British forces drop around 1.5 million tons of

bombs on Germany.

A single raid

could see up to 1,000 planes

unleash their fury on German cities.

So Hitler moves underground,

building impregnable mega structures across

occupied Europe.

The Germans built a whole series of structures that were

immune to all the bombs that the British had then developed.

The most famous of these were the submarine pens on

the French coast at Saint-Nazaire,

with concrete ceilings 10 feet thick.

NARRATOR: To break through, Britain needs

somewhere to test experimental bombs in secret.

Empty by order of William the Conqueror,

the remote New Forest is ideal.

This LIDAR image shows an essential

part of the Ashley Walk Bombing Range.

NARRATOR: According to declassified military records,

Ashley Walk becomes operational in 1940.

Hell is soon raining down onto vast chalk circles.

MORGAN: The concentric circles in the image

were a method of evaluating the effectiveness of extremely

powerful bombs.

You can measure the distance from the epicenter of

the explosion, and it allows you to determine

just how effective the weapon is going to be.

The most important person involved in this

testing was the legendary scientist Barnes Wallis.

Dr. Wallis masterminds the revolutionary bouncing bomb,

tested at Ashley Walk,

which wipes out two German power stations beyond the reach

of conventional ordnance.

HYMEL: Thanks to Barnes Wallis, these so-called

impregnable defenses are no longer impregnable.

And Dr. Boom is just warming up.

There's only one bomb that I can think of that had enough

power to generate a crater like this,

and that is a Tallboy.

NARRATOR: Wallis's six-ton Tallboy is a game changer.

WALTERS: It really was a big bomb.

In fact, it was what was known as an earthquake bomb.

The earthquake bomb didn't need precision.

It set off such giant shockwaves that it would

destroy targets for hundreds,

if not thousands, of yards around.

NARRATOR: The Tallboy, tested at the LIDAR site,

is first deployed in June 1944.

854 will fall by

the end of the war,

wiping out bridges, dams, and V-1 launch sites.

ANNOUNCER: We see the Tirpitz firing

back at them with 15-inch guns.

NARRATOR: Tallboys also sink

Hitler's prime battleship, the Tirpitz.

ANNOUNCER: Watch for the 12,000-pounder

that stopped those guns once and for all.

NARRATOR: While at the New Forest,

Wallis is preparing to test something even bigger.

I mean, look at this extremely

heavy duty concrete and this rebar here.

Really designed to take a hit.

I'm willing to bet that another type of earthquake bomb

was also being tested here, and that's called the Grand Slam.

NARRATOR: Weighing more than some tanks,

the Grand Slam is nicknamed Ten Ton Tess,

and she's devastating.

The Grand Slam was only tested once before

it was used over Nazi Germany, and it was tested here in

the New Forest,

and that was one of the biggest explosions that's ever

happened in the British Isles.

NARRATOR: On March 13th, 1945,

an experimental Grand Slam smashes into the targets on

the LIDAR image at 700 miles an hour.

Nine seconds later, it explodes, triggering a massive

artificial earthquake.

SILBEY: The test of the Grand Slam bomb

was so successful, the Allied High Command decided to send

the bomb into action the very next day.

They took out viaducts, coastal defenses,

even submarine pens.

The Germans didn't know what hit them.

They thought their sub pens

and their batteries were completely impregnable.

The Grand Slam bomb was incredibly effective at

destroying Nazi architecture

and infrastructure and really helped turn the tide of

the war.

SILBEY: As soon as the Americans saw the success of

this new kind of British weapon,

they created their own version, the T-12 Cloudmaker.

NARRATOR: Twice the size of the Grand Slam,

the 20-ton Cloudmaker never sees action,

as it is quickly superseded by nuclear weapons,

but earthquake bombs make an earth-shattering

comeback in the run up to the 1991 Gulf War.

Iraqi despot, Saddam Hussein, has read Hitler's playbook

and built a fortified mega bunker underground.

The United States deploys this new weapon called the GBU-28,

which is gonna become known as the bunker buster.

SILBEY: The GBU-28 destroyed the Iraqi bunker.

At its basic level,

it was identical in effect to what Barnes Wallis

had started back in the Second World War.

I don't want to imagine a World War II

that didn't have a Barnes Wallis on our side.

I put him up there with, like, Alan Turing, for example.

These people who, through genius,

helped to win the war.

NARRATOR: Barnes Wallis's genius and the secrets of

the New Forest have been exposed from the skies.

But what else lurks beneath these

ancient woodlands remains to be discovered.

Given the top secret clandestine nature of

this site, it may be that we never know.

NARRATOR: Coming up, the wrath of the female super soldiers.

HORTON: They were disciplined, organized,

and highly successful.

And mummies, Romans, and biblical plagues.

And that's what we're seeing from satellite.

NARRATOR: June 30, 2019.

Eyes in the sky over Egypt

scan a valley 50 miles northwest of Cairo.

We're seeing a beige ground, what you'd expect to see,

but then in the middle is this strange shape.

KOUROUNIS: It almost looks like some gigantic footprint has

just come down and smashed into the desert.

NARRATOR: The mega-sized print covers around

eight million square feet of the valley floor.

It's as if the earth has been bleeding,

but the wound closed up and dried.

KOUROUNIS: Looking a little closer,

it has all the characteristics of a dried lake bed.

It's not just the shape that's unusual,

it's the color.

Maybe we're seeing some mineral that was

left over when the lake dried up.

NARRATOR: Historical records confirm the presence of

a unique mineral in the lake

that could partly explain its weird coloration,

one that played a key role

in the two greatest civilizations of antiquity.

It just so happens that this lake is covered

in a layer of sulfate deposits known as natron.

NARRATOR: Some 5 and a half thousand years ago,

the ancient Egyptians begin mummifying their dead.

They encase the cadavers in natron, harvested from

the country's desert lakes,

to dry out the corpse, preserving it for the afterlife.

These natron lakes are very alkaline,

meaning these are harsh to most forms of life, and that's

what we're seeing from satellite.

NARRATOR: Natron from the lake

in the image was likely used to entomb many of the great

pharaohs and high priests of ancient Egypt.

During the reign of Cleopatra,

Egypt falls under the rule of Rome, and the mineral is

put to a very different use, one that transforms the world.

The sailors were using natron blocks to support

their cooking pots on the beach, and the heat

of the flames caused the blocks to melt,

producing glass.

And as these little streams of glass

are coming out from under the fire, boom,

the glass industry is born.

NARRATOR: For much of antiquity,

glass was as expensive as gold and precious gems,

an indulgence reserved for chieftains,

royalty, and religious buildings.

The very first glass is believed to

have been made in Mesopotamia 5,000 years ago.

That early period is almost done with a small scale.

NARRATOR: In around 30 BC,

the natron deposits in the lake attract

Roman scientists,

alchemists in glass making,

who set up vast furnaces around its shores.

Glass is mainly sand, and there's

plenty of that out in the desert.

Finding that resource, no problem, but you need

a flux catalyst.

That's exactly what we find here at this lake.

It was the Romans that industrialized glass production

on a much bigger scale,

as glass then became a consumer object that was

employed throughout the empire.

NARRATOR: Such is the value of Roman glass

that it is traded across the known world,

reaching as far as Afghanistan and China.

We're not talking about, like, some artisan making a couple

of glasses, we're talking about glass slabs

weighing 20 tons that could be shipped anywhere.

NARRATOR: The advent of glass blowing enables the Romans to

form these giant blocks into any shape or size,

revolutionizing the industry.

A single glass slab manufactured from this site in

Egypt could have been broken down

into thousands of pieces and turned into tens of thousands

of individual bottles and glasses.

HYMEL: It makes it cheaper and more accessible

to a much larger population -- it just explodes.

NARRATOR: For around 400 years,

the site spotted from space

is the focal point of Roman glass production,

creating the windows that adorn Rome's greatest buildings.

And putting bottles on the tables of the empire's

65 million citizens.

Yet the presence of natron only explains

part of the lake's strange appearance.

HORTON: Natron is a mineral salt that's naturally

white or pale yellow.

So that raises the question,

what is this red deposit that's also found on the lake?

NARRATOR: Mark Horton learns that the caustic waters

that enticed the morticians and glass makers

of Egypt and Rome also attract aquatic

organisms in their countless billions.

On the surface of this lake is an algae that can live in

these extremely hostile environments

and breeds and forms this skin of pinky red on

the surface of the white salt.

NARRATOR: When the algae blooms, it produces red pigments,

creating giant patterns on the natron lake.

These blooms also generate toxins, which are lethal

to fish, birds, and humans,

toxins which could help explain one of

the most famous mass deaths in history.

There are Biblical stories that speak

of a similar phenomenon.

God sent 10 plagues upon Pharaoh and the Egyptians,

and one of those was to cause the Nile to run blood red.

BELLINGER: The fish died, the river stank,

the Egyptians couldn't drink the water anymore,

and it all happened just a few miles from where

this image is located.

NARRATOR: The same lake that helped mummify

the Egyptians, carrying them to the afterlife,

may have also been the cause of their sickness and death.

Lots of legends are based on nuggets of truth, and it's

entirely possible that the Biblical tale

of the Nile running red could have been caused by one of

these massive red algal blooms.

NARRATOR: Coming up, attack of the man hunters.

The Europeans are utterly terrified of

these women warriors, whom they called Amazons.

NARRATOR: And the Nazis' secret terror weapon.

12,000 tons is enough to kill millions and millions

of people.

NARRATOR: October 12th, 2020.

A satellite scanning the country of Benin

in West Africa

captures strange features in a lake far below.

This is bizarre.

I don't see any roads, I don't see any fields,

just homes, buildings, and water.

It looks like a settlement that's

just been overwhelmed by an incoming flood.

HORTON: But looking more carefully, I can see

that this is not a flooded village,

but actually a village that's been built

deliberately in a lake.

NARRATOR: This is Ganvie, a giant floating village of some

3,000 raised structures and the ancestral home

of the Tofinou people.

Yet what really intrigues analysts is why the Tofinou

chose to build it here in the first place.

BELLINGER: The Tofinou tribe has, for generations,

been building over water,

and we know from oral tradition that's for

an extraordinary reason.

NARRATOR: The story of the strange lake village

begins in the 17th century.

At the time,

much of this region is dominated by the Tofinou's rivals,

the Fon people, who ruled the powerful Dahomey kingdom.

It was actually sometimes referred to as the Sparta

of Africa, because this was a society of brutal warriors.

Fon warriors developed a fearsome reputation that

traveled far beyond the borders of their kingdom.

NARRATOR: The Fon rely heavily on forced labor,

and around 1/5 of their kingdom's

one million strong population are slaves.

This group of people use this military brutality and prowess

to become very wealthy and successful in the slave trade,

terrorizing any of the tribes around them that they did not

have a relationship or an agreement with.

HORTON: They were disciplined, organized,

and highly successful.

NARRATOR: In 1720, the Fon warriors push

south towards the site in the image,

putting their king in contact with European slavers.

In exchange for goods and weapons,

he supplies them with around 20 percent of

all the humans trafficked across the Atlantic.

But years of raiding neighboring states

deplete the number of male Fon warriors,

and the kingdom's enemies begin to close in.

This creates a cultural shift for the Fon people

and through that,

their women become more and more a part

of their combat force.

Women played a major role in the military,

so much so that the king had an elite group that served as

an all female royal guard.

NARRATOR: Such are the skill and ferocity of

these female warriors that between the 1760s and 1840s,

their ranks increase from 600 to 6,000.

They're the only known female fighting

force in the world at this time.

The Europeans are utterly terrified of

these women warriors, whom they called Amazons.

Their specialty was pre-dawn attacks on enemy villages,

and that was the most efficient

and effective way for them to gather up slaves

to sell to the Europeans.

NARRATOR: The Fons' slaving raids puts them in conflict with

the Tofinou people and explains the construction of their giant

lake village in the satellite image.

The Tofinou people didn't have quite the warrior culture that

the Fon did, but they were clever,

and they were observant, and over time,

they look for weaknesses in the Fon tactics and strategy.

One of the weaknesses they found was a fear of the lake.

NARRATOR: The Tofinou know that the Fon are

devotees of Vodun, the origin of today's Voodoo.

They believe that powerful, supernatural beings

inhabit nature and fear vengeful water spirits.

According to Fon tradition,

a powerful demon walked the waters of this lake,

and they would never do anything to raise that demon's anger.

KOUROUNIS: The Fon refused to attack

any structure that was on water,

so the Tofinou built their village on the water,

and suddenly, they were able to use their own superstition

against them.

NARRATOR: Over the following decades,

more Tofinou move on to the lake

to escape persecution at the hands of the Fon.

They become known as the Water People.

KOUROUNIS: As long as they lived on the water,

these villagers were safe from attack

and were able to avoid being sold into slavery.

They gave the name of the village Ganvie,

which means, in the local language, "We survived."

BELLINGER: And so the Tofinous stayed and continued to build

and expand this village on stilts

for many generations to come.

NARRATOR: 150 years after the end of the slave trade,

the water village of Ganvie continues to flourish,

a living monument to one people's resilience in

the face of unspeakable terror.

JANULIS: To this day, there are 20,000 Tofinou

still living on the lake, just like their ancestors did,

who avoided being captured by the Fon.

It's a very interesting, very horrific history,

but one that needs told.

NARRATOR: Coming up, monster tank face off.

It was one of the most incredible battles

of World War II.

NARRATOR: And the killer quarry.

It becomes a warehouse of death.

NARRATOR: October 9, 2018.

A camera in orbit over Ukraine scans the city of Kharkiv.

WALTERS: What we're looking at here

is a pretty grim-looking industrial complex,

bit of a wasteland, frankly --

it's not a very inviting place.

NARRATOR: Yet lines of objects hidden between

the desolate looking buildings do invite attention.

CAVELL: Looking closer, you can start to see

that these objects actually have

some kind of a turret on them and some sort of gun.

These are tanks.

These are armored fighting vehicles,

and there are dozens and dozens of them.

NARRATOR: Leaked photographs confirm that the image

has captured a monstrous metal graveyard,

containing the rusting remains of hundreds of tanks.

WALTERS: You've got to ask yourself why are there

so many tanks just sitting there doing nothing.

Tanks should be out fighting.

This is just a huge tank park.

NARRATOR: Martin Morgan studies the city's history for clues.

When I look into original records,

I find that this is the old Kharkiv tank factory.

This was the largest factory for the production of armored

fighting vehicles during the old Soviet Union

and the birthplace of what was one of the greatest

fighting machines of the 20th century.

NARRATOR: That fighting machine is the T-34 tank.

The T-34 tank is one of the most powerful weapons that

the Soviets wielded on

the battlefields of the Second World War.

It's a part of every battle.

It's a part of every Soviet victory,

and they're all made at Kharkiv.

NARRATOR: The T-34's engine and tracks are built to handle

mud and snow on the battlefields

of the Eastern Front.

What's more, it has a more powerful cannon and better

armor than German tanks,

but it's light enough to outpace them

on the battlefield.

MORGAN: The T-34 is arguably the finest tank of

the Second World War, because it is the best of both worlds.

The Germans were scared as hell of this vehicle,

and that speaks to just how effective

the design really was.

NARRATOR: The success of the T-34

forces the Nazis to deploy the massive 54-ton Tiger.

In July 1943, vast numbers of Russian and Nazi

tanks meet head-on at the Battle of Kursk.

About 5,000 tanks will come to this battle.

So it's the biggest tank battle of all time,

including up to today.

You have tanks just rolling towards each other, firing

massive shells back and forth.

I mean, it was -- it was probably one of the...

most incredible battles of World War II.

NARRATOR: At the Battle of Kursk,

the Russians incur devastating losses,

but the T-34s ultimately prevail.

The Germans never recover from this defeat,

and two years later, the Soviets capture Berlin.

PAVELEC: Kursk is one of the turning points that

solidifies the final retreats

and absolute route of the Germans

off of the Eastern Front.

NARRATOR: Following the end of World War II,

the Kharkiv Tank factory continues to play a vital role

in Soviet military strategy.

MORGAN: There are over 60,000 workers that are producing

about 60 tanks a month at this facility

during the height of the Cold War.

[indistinct shouting]

NARRATOR: In 1991, the Soviet Union collapses,

and countries like Ukraine gain their independence.

Tanks stopped rolling off

the Kharkiv factory line, and its yards begin filling with

mothballed relics of the country's communist past.

Yet recent analysis has revealed renewed activity

at the site.

MORGAN: When we look at satellite imagery,

we can see that tanks are kind of coming and going from

the facility.

NARRATOR: It appears Ukraine has once again turned to

the T-34 tank factory to help it repel a foreign threat.

These tanks could well be part of Ukraine's

absolutely justified efforts to defend herself against

Putin's aggression.

NARRATOR: In 2014, Russian President Vladimir Putin

[speaking Russian]

orders his troops to invade Ukraine's Crimean Peninsula.

This triggers an ongoing war,

which has claimed over 13,000 lives.

The attack that Russia mounts on the Crimea is forceful.

They come in with aircraft.

They come in with tanks, they come in with ground troops.

NARRATOR: In a twist of fate,

Russia is now fighting tanks from the very factory

that helped it to defeat Hitler all those years ago.

MORGAN: This image is full of deep, contemporary ironies,

because it makes you confront the way that the former

Soviet Union crumbled, fell apart,

and the awkward, intense new world that has been

created in its aftermath.

NARRATOR: Coming up, magic lake.

It's as if the water had been turned to oil.

NARRATOR: April 2017.

Satellites orbiting over northern Europe

scan a quarry in England's industrial heartlands

and uncover a mystery.

RUBEN: We're looking at what

looks like a rather beautiful lagoon,

very vibrant blue.

And then you go to the next image,

and it's black.

NARRATOR: The lagoon is vast,

43,000 square feet,

but its dramatic color change has taken just a few hours.

It's as if the water had been turned to oil.

That's what it looks like.

NARRATOR: This quarry is called Harper Hill,

and it has a dark history that could explain the lagoon's

weird transformation. -PAVELEC: Interestingly,

this was a chemical weapons storage facility before, during,

and after the Second World War.

Tens of thousands of chemical weapons were stored here and in

the area surrounding it.

NARRATOR: In 1938, Harper Hill Quarry

is chosen as the location

for a facility code-named Maintenance Unit 28.

Over the following two years,

the British military use it to conceal more than 45,000

different chemical weapons.

It becomes a warehouse of death.

By 1940, it's the largest chemical

weapons storage depot in Britain.

NARRATOR: The warehouse of death has its origins in the mud,

blood, and gore of the battlefields of World War I.

JANULIS: World War I was the first example

of truly industrial warfare,

and in 1915, the first example of

chemical warfare being utilized.

During World War I, chemical weapons

kill or injure over a million soldiers,

including a young Adolf Hitler.

After World War I, the Western countries decided

that chemical warfare was so inhumane,

it should be banned,

but that didn't stop all of these countries

from continuing to experiment with chemical weapons.

NARRATOR: In 1938, German scientists discover sarin,

a compound 20 times more lethal than cyanide.

They go on to produce 12,000 tons of the nerve agent

during the war.

12,000 tons of sarin gas is enough

to kill millions and millions of people.

So places like Harper Hill acted as

that storage point for the captured chemical weaponry

at the end of World War II.

PAVELEC: Could it be that there's chemical weapons

that were not disposed of properly

that are now coming to the surface and turning

the water black?

NARRATOR: When scientists test the lagoon

in the image, they confirm it is dangerously contaminated,

but it's a legacy of a different era

in the quarry's history.

Chemical analysis has shown that it's

actually got a really high pH level.

KOUROUNIS: It's been measured at a pH of 11.3.

Pure ammonia is about 11.6.

So this is nasty stuff.

NARRATOR: Long before World War II,

the quarry produced vast amounts of highly alkaline

quicklime.

During the 19th century,

it played a vital role in creating the modern world.

JANULIS: Quicklime reacts with certain elements

within molten metal,

basically getting the impurities out,

causing them to aggregate, creating slag that can be

easily removed to get pure steel.

NARRATOR: Steel made using quicklime fuels

what is known as the second Industrial Revolution,

which transforms the industries and landscapes of

England, the U.S., and beyond.

MORGAN: So many of the things that we recognize as being part

of the greatness of modernity are created during

this critical time period,

during the Industrial Revolution.

NARRATOR: In 1952, the quarry closes,

and it fills with water,

creating the lagoon in the image.

That begins to explain a lot about the color of this water.

That deep blue can come from calcium carbonate

that leaches out of limestone.

KAYS: Now we understand why it's so beautifully blue,

nut the question remains, why did it suddenly turn black?

NARRATOR: As news of the azure lagoon spreads,

it attracts thousands of visitors, and its caustic waters

become fetid with all manner of garbage and waste.

RUBEN: The blue color is really beautiful,

but this lagoon has also been used as a dumping ground for

the bodies of animals, car wrecks,

whatever people have decided to throw in there.

KOUROUNIS: The authorities actively try to dissuade people

from swimming in these waters,

but all of the signs and warnings have little effect.

So what do you do?

Well, the authorities have gone to the extreme

steps of having to dye the water black.

KAYS: They bought some dye.

They dumped it in, the next day, when the revelers showed up to

hang out by their beautiful,

toxic blue lake, they found the water had completely

changed color and was not nearly as inviting.

The lesson here is

just because something looks beautiful,

that doesn't mean you should immediately

expose your entire body to it.