Original subtitles

[upbeat dramatic music]

- [Narrator] We are surrounded

by extraordinary feats of engineering,

constantly pushing the boundaries of what's possible.

- Without engineering, there'd be no modern world.

- [Narrator] Gigantic cities,

amazing infrastructure,

and ingenious inventions.

- Engineering is the key to turn dreams into reality.

- [Narrator] To reach these dizzying heights,

today's technology relies on breakthroughs

made by ancient engineers.

- It's mind-boggling how they did this.

- [Narrator] How did early civilizations

build on such a scale?

- They raised the bar for construction

in a way that no one thought possible.

- The sheer engineering ability is in itself impressive.

- [Narrator] By defying the known laws of physics

and daring to dream big,

they constructed wonders of the world

from gigantic pyramids

to awe-inspiring temples

and mighty fortresses.

All with the simplest of tools.

- Cannot imagine the skills

people would have needed to build like this.

- [Narrator] Now it's possible to unearth the secrets

of the first engineers.

- They managed to construct edifices

that have survived the ravages of time.

- [Narrator] And reveal how their genius

laid the foundations for everything we build today.

[upbeat dramatic music continues]

[upbeat electronic music]

[water bubbling]

Water. [water splashing]

A matter of life or death.

[upbeat electronic music continues]

- Water is the one thing none of us can do without.

- Without water, nothing would be possible.

- We can't survive more than about three days without it.

[water splashing]

- [Narrator] A modern city like New York

consumes over 1 billion gallons of water every single day.

Keeping the taps on

ensuring a constant flow of clean, safe water

has been one of the greatest engineering challenges.

- When you turn on a tap,

it's so easy to forget the immensely complex engineering

which makes that fresh water possible.

- [Narrator] Engineers have built vast underground tunnels,

diverted rivers, constructed mighty dams.

- The careful balance struck between the forces of nature

and the engineering required to build a dam

is pretty astounding.

- [Narrator] Giant infrastructure dominating the landscape.

[upbeat electronic music continues]

Huge pumping stations.

Aqueducts defying gravity to carry water hundreds of miles.

Machinery to turn salt water into fresh.

And incredible irrigation systems

bringing arid deserts to life.

Despite all this innovation,

the world still faces a water shortage.

[loud crackling]

Population growth, agriculture,

and industry drive ever increasing demand

for this priceless resource.

- There's more than 2 billion people

who don't have enough water at the moment.

This problem is only going to increase.

- Water will continue to be a scarce and precious resource.

- [Narrator] Thousands of years ago,

a smaller global population

meant finding water sources wasn't usually such a problem.

But developing ways to control and transport water

would require a great leap in human ingenuity.

[soft upbeat music]

So how did ancient engineers invent the technology

that led to the birth of agriculture

and allowed ancient empires to expand?

[air whooshing]

[soft relaxing music]

For early civilizations, the simplest way to obtain water

was to build close to it.

- Throughout history, settlements

have tended to be by rivers

simply because it means you've got water easily accessible

but also it's likely that the land next to the river

is going to be capable of cultivation.

- [Narrator] But as settlements developed,

living beside water wasn't always an option.

New technology was needed.

In the 7th century BC, the ancient Greeks

were one of the first to tackle the problem

by building large civic water systems.

[soft relaxing music continues]

One of Greece's main maritime hubs

was on the wealthy island of Samos.

And Samos had a problem, a bone dry climate.

- One thing that its population were really lacking

was access to clean, safe fresh water.

- [Narrator] According to legend,

engineers were tasked with bringing water

to the island's main port city of Tigani.

- The basic problem was the nearest source of fresh water

lay miles away over a mountain.

[dramatic orchestral music]

- [Narrator] An architect and engineer called Eupalinos

was commissioned to get the job done.

Using simple measuring equipment and complex mathematics,

he came up with an amazing engineering plan.

Something never previously attempted.

- He decided that he needed to go through the mountain,

bore a tunnel that would go underneath all that rock.

- [Narrator] It would mean digging for just over 1/2 a mile

through solid rock.

The idea was to excavate simultaneously

from both sides of the mountain.

- Building a tunnel from either end

is an incredible technological challenge.

- [Narrator] But ensuring both sides met inside the mountain

was no mean feat.

- Eupalinos took two crews of engineers

working on either side of the mountain

with hammers and chisels,

cracking through the hard limestone to meet in the middle.

- [Narrator] Although rumors of this technological marvel

persisted, it was only rediscovered around 170 years ago.

And recently some of its secrets have come to light.

In the 1970s, German archeologists

spent three years excavating the entire tunnel

and connecting aqueduct.

According to their measurements,

it was built over 570 feet below the summit of the mountain

and was around 3,400 feet in length.

It was proof of Eupalinos's legendary achievement.

But how had it been built?

[tools banging]

It involved more than brute force.

[tools banging]

This called for precision surveying.

- If you imagine you've got two tunnels

coming towards each other,

and if they were in parallel,

they could very easily miss each other.

- [Narrator] For Eupalinos, the key lay with mathematics.

- He understood through geometry

that if you angle both tunnels in the same direction,

eventually their paths will cross.

They will absolutely meet,

there's no doubt in that mathematically.

- [Narrator] It worked.

After nearly 10 years' back-breaking effort,

the tunnelers finally met in the middle.

They'd excavated well over 15,000 tons of rock

and laid 5,000 sections of clay pipe.

Once completed, abundant, fresh water

began to flow through the city's fountains

and continued to do so for over a thousand years.

[dramatic orchestral music]

[water splashing]

- Today, we have GPS

and we have all sorts of laser measurement systems,

but he didn't have any of those tools at his disposal.

So it's absolutely incredible that he succeeded.

- [Narrator] Eupalinos had earned his place

in the annals of engineering.

Even today, engineers can struggle to ensure

the water keeps flowing.

[soft relaxing music]

In 2008, the Mediterranean island of Cyprus

suffered a fourth consecutive year of low rainfall.

By summer it faced a full-blown drought.

[insects chirping]

So how could the authorities ensure

water reached residents

and the millions of tourists flocking there for holidays?

At first, water was shipped in from Greece using tankers

but this wasn't viable in the long-term.

So in the Turkish North of Cyprus,

engineers came up with an ambitious plan.

- They decided to pipe water 50 miles from the mainland

across the sea to the island.

[upbeat pulsing music]

- [Narrator] How could it be done?

First step was to build a massive new dam in Turkey,

creating a reservoir holding over

4.5 billion cubic feet of water.

- Then came the construction

of the longest underwater subsea pipeline in the world.

- [Narrator] Engineer's first built anchor platforms

weighed down on the seabed.

Then they attached to ropes with buoyancy aids,

enabling the 50 mile pipeline

to be suspended above the seabed.

At 820 feet down,

it was safely below fishing stocks

and shipping lanes.

Water from the reservoir in Turkey

was then pumped through the pipeline to Cyprus.

As a result,

the water supply to Northern Cyprus was guaranteed.

But for one ancient civilization across the sea from Cyprus

water supplies were never a problem.

[air whooshing]

[soft relaxing music]

Admired for its great advances

in every area of human endeavor,

from the arts to science, technology to religion,

its engineering accomplishments include great monuments,

pyramids, and temples.

Ancient Egypt.

Egyptian civilization developed

along the banks of the River Nile.

Each year around July,

the Nile would flood, spilling over with water,

flowing down from mountains in the south.

[water splashing]

As the waters receded,

they left behind rich soils

allowing agriculture to flourish.

The extent of the yearly inundation

determined how much food would be harvested that year.

But flood levels were always unpredictable.

- Too low, not enough fertilization,

therefore, your crop is inadequate.

Too much and you end up sweeping away towns

and also ruining the fields.

- [Narrator] So how did Egyptian engineers

prepare for either feast or famine?

In 2016, workers constructing

the foundations of a water pumping station

near the ancient city of Thmuis

uncovered a mysterious structure.

[soft pulsing music]

Made from large limestone blocks,

it was a circular well roughly eight feet in diameter

with a staircase leading down into its interior.

Archeologists inspected the site

and realized it was part of a rare structure

called a nilometer.

- Nilometer was the way in which

the ancient Egyptians measured the flood of the Nile.

- [Narrator] These nilometer wells

were frequently located within the confines of temples

where only the priests

and rulers had access.

How could they help predict the coming harvest?

- Okay, a nilometer is effectively a shaft

connected to the Nile by a little tunnel.

And on the sides of it, you put markings

and you look and see how high the water's come up that shaft

and read off the numbers.

[upbeat orchestral music]

- [Narrator] Over many years,

flood levels would have been recorded.

- They then presumably looked at tables

drawn up over history

and be able to work out where there would be a good harvest,

bad harvest, or indifferent harvest.

- [Narrator] This secret knowledge

was a source of power in ancient Egypt.

[rocks crashing]

In the early 1970s,

Egypt's era of inundations finally came to an end

when the Aswan High Dam became operational.

Fully controlling the annual flood,

it ensures water is now available for irrigation

all year round.

The dam has almost doubled Egypt's agricultural yield

while improving navigation across the Nile,

a boon to the fishing industry and tourism.

It also provides half of the nation's power demands.

Dams have been in use for over 5,000 years.

Today, there are over 58,000 of them worldwide.

China has the most and recently completed

one of the biggest in the world, the Three Gorges Dam.

[upbeat electronic music]

It's around 600 feet high,

more than 7,500 feet long,

and creates a reservoir with a surface area

of around 400 square miles.

To pull off this dazzling feat of engineering,

engineers had to overcome a major problem.

- One of the biggest challenges

that engineers faced in building this dam

was that it's still a really major waterway

and they had to find a way to allow ships to pass.

- [Narrator] When the dam first opened,

ships used a series of locks to pass.

But this added three or four hours to journey times,

so engineers were tasked with finding a better solution.

Result? The world's largest elevator for ships.

Vessels enter a reinforced concrete chamber

suspended from 256 cables attached to counterweights.

- You sit the ship in a kind of lift car

that's actually a big bucket of water.

- [Narrator] When the counterweights go down,

the chamber rises, or vice versa.

At the top and bottom of the lift

the chamber sits at the same level as the river.

So when its steel gate opens, a vessel can exit,

cutting the time a ship takes to pass the dam

to just 40 minutes.

This brilliantly engineered solution

is one key to the dam's success.

The other is its hydroelectric output.

- The Three Gorges Dam

is an unbelievable feat of engineering.

It produces so much power,

22,500 megawatts.

- [Narrator] That's enough electricity to power

both New York and Los Angeles every day.

But dams can also have a negative impact.

Flooding large areas, forcing people to relocate,

and impacting ecosystems.

[water splashing]

Dams weren't the only means of controlling water

in the ancient world.

Engineers also came up with other ingenious devices.

[loud crackling]

[soft orchestral music]

Although the Nile inundation

provided rich soils in which to grow crops,

the farmers of ancient Egypt still needed

a constant flow of water to reach their plants.

But how could this be guaranteed once floodwaters receded?

Canals and ditches were dug out from the river

leading into the fields,

but engineering solutions were needed

to then carry water to the crops.

One such device was the shadoof,

first used for irrigation in around 3000 BC.

- A shadoof is basically a beam of wood

on a balance in the middle

with a bucket on one end and a counterweight on the other

so that you could easily lift quite heavy volumes of water

up to a higher level.

- [Narrator] When correctly balanced,

the counterweight supports a half-filled bucket.

It takes a bit of labor to lower when empty,

but only minimal effort to lift a full bucket.

Due to its simplicity, the shadoof is still used today

in some countries for irrigation.

But there are certain parts of the world

where agriculture has never been viable,

and they're growing fast.

[loud cracking]

[farmer whistling]

- Due to climate change,

we're seeing more and more arable land

turning into desert every year.

[soft pulsing music]

- [Narrator] Yet thanks to modern engineers,

in some places the desert is now blooming.

And the best place to observe this transformation

is from space.

[soft pulsing music continues]

From orbit, strange circular forms are starkly visible

in some of the world's driest regions.

- When you see these green spots in the stark desert context

it's very striking and very unusual.

It looks very out of place.

Apparently astronauts aboard the International Space Station

use them as landmarks.

- [Narrator] These circular areas are in fact crops.

But how can they grow in the middle of a desert?

It relies on an engineering solution

called center pivot irrigation.

[cheerful upbeat music]

[water splashing]

- Pivot irrigation is essentially a system

where you look for water deep under the ground.

So it could be up to four kilometers deep.

And these are really, really ancient sources of water

that have been there for thousands of years.

- [Narrator] Once pumped to the surface,

water flows along an irrigation arm

powered to move around in a wide circle.

- Water sprayed in very specific size droplets

that can be controlled to be accurate,

depending on the crop requirement.

- [Narrator] This method wastes less water.

Crops receive just the right amount

to enable them to flourish.

[cheerful upbeat music continues]

[water splashing]

Some scientists are concerned center pivot irrigation

may deplete deep water reserves.

But there's no doubt this engineering

is transforming some of the world's driest regions.

Getting water to where it's needed most

has always been an engineering challenge.

Nowhere more so than for one ancient city

with a population of over a million thirsty souls,

all in need of fresh water.

[enchanting orchestral music] Ancient Rome.

Roman engineers were renowned

for their ability to control the flow of water.

[water splashing]

Digging deep tunnels to transport it many miles.

Building mighty structures across ravines and valleys

to keep it flowing.

[dramatic orchestral music]

Constructing luxurious heated public baths

and lavish fountains.

- The Romans developed amazing water control technology.

This massive network of interconnecting

sewers and aqueducts and drains.

[dramatic orchestral music continues]

- [Narrator] Roman techniques for the collection,

storage, and delivery of water

over huge distances were unsurpassed.

Their engineers developed a host of innovative technologies.

- The Romans are the masters of providing water

wherever and whenever it's needed.

- [Narrator] But why go to such lengths?

- Like their famous road network,

controlling water allowed the Romans

to develop and supply their rapidly increasing population.

- The Romans knew that water was fundamental

to the success of their civilization.

- [Narrator] Without a reliable water supply,

the entire continent-spanning empire could be threatened.

- A couple of days with no water, you have complete anarchy.

- [Narrator] But what were the technological breakthroughs

that kept water flowing throughout the Roman empire?

[water splashing]

[pulsing orchestral music]

By the 2nd century AD,

ancient Rome had become the largest city in the world.

Home to well over a million people.

To expand further, it desperately needed a constant,

safe, and guaranteed supply of water.

- Rome is built on the River Tiber

and the Tiber provides some water,

but as Rome expands,

as it becomes one of the greatest cities in the world,

it needs to find additional fresh water from elsewhere.

- [Narrator] So where did this additional supply come from?

A vital clue was found

during construction of the city's Metro.

[subway whirring]

- It's one of the smallest in Europe.

And part of the reason for this

is because the ground underneath the city

is so rich in archeological remains.

Every time a new tunnel is planned,

they have to excavate more area

and discover more things which have to be investigated.

- [Narrator] In 2016, while extending one of the lines,

workers stumbled across some impressive remains

over 100 feet in length.

After careful analysis,

archeologists concluded they were part

of the oldest known Roman aqueduct, dating back to 312 BC.

- The first aqueduct to be built in Rome is the Aqua Appia

which was built by the censor at the time,

Appius Claudius Caecus.

- [Narrator] At this early point in its history,

Rome was at war with a tribe from Southern Italy

called the Samnites.

- The Romans feared that the Samnites

might pollute the River Tiber,

which was their main source of water.

- [Narrator] But the city's nearest alternative supply

was a natural spring around 10 miles away.

[water splashing]

Without the aid of mechanical pumps,

how would engineers bring this water to Rome?

[dramatic orchestral music]

- The solution was to build an aqueduct,

to rely on gravity, to create such a gentle slope

that that water would trickle

all the way into the city itself.

- [Narrator] The Aqua Appia

was built with an incredibly shallow gradient.

less than half a degree of descent.

It was a great test of engineering skill.

Too much of an incline, and the fast-moving water

would erode the fabric of the aqueduct.

- Too little of a slope, than the water itself

can remain stagnant,

so it's an incredible engineering challenge.

- [Narrator] To get there gradient just right,

engineer's used a device called a chorobates.

Similar to modern spirit levels,

it was a bench with attached plumb lines

and a groove carved into the middle containing water.

Two site holes at each end

enabled a measurement to be taken using a ranging pole

around 40 feet away.

By raising and lowering the legs of the bench,

the surveyor was able to plot the gradient of the aqueduct.

But the aqueduct also had to be protected

from possible attack.

So the Aqua Appia would be constructed mostly underground.

[tools banging]

To do this, the Romans used the so-called qanat method.

Well-like shafts were dug at consistent vertical intervals

until they reached the desire depth.

Cranes using pulley systems

were used to lower building materials in

and debris from the tunnels out.

Workers then dug horizontal sloping tunnels,

linking the adjacent shafts together.

And it worked.

[dramatic orchestral music continues]

The Appia supplied the city of Rome

with an estimated 16 million gallons of water per day.

[dramatic orchestral music continues]

[water splashing]

- There were around 700 taps in the city

and about 200 of those were used for private purposes.

And the rest of those taps were for public use

for public baths, for fountains,

and for draining the streets of Rome.

[soft enchanting music]

- [Narrator] Over a period of around 500 years,

a total of 11 aqueducts were built

bringing water to Rome from up to 60 miles away.

To this day, the Aqua Virgo,

an aqueduct constructed in 19 BC,

supplies water to one of Rome's most famous landmarks,

the Trevi Fountain in the heart of the city.

[fountain splashing]

[water splashing]

[relaxing orchestral music]

As time went on, the Romans constructed further aqueducts.

Some amazing feats of engineering right across the empire.

- Romans took their water engineering prowess with them

wherever they went, creating magnificent structures

from Spain to Syria,

showing off not only their technical brilliance

but the amazing power of water itself.

- [Narrator] Many structures still stand today,

testament to the prowess of ancient engineers.

The Segovia aqueduct in Spain

was built during the second half of the 1st century.

[dramatic orchestral music]

While the Valens aqueduct reached over 150 miles in length

and provided water to Constantinople, modern day Istanbul.

But one of the most impressive structures of all

was built as part of an aqueduct found in Southern France

near the town of Nimes.

The Pont du Gard.

[dramatic orchestral music continues]

- The Pont du Gard is a Roman aqueduct bridge

built in the 1st century AD.

It remains an amazing spectacle of Roman engineering.

- [Narrator] Designed to carry water over the River Gardon,

this marvel stands 160 feet high

and features three vertical rows of arches.

So how did engineers build

one of the tallest of all Roman structures?

[air whooshing] [tools clanging]

Numerous scientific studies have revealed

that an impressive volume of rock was needed

to complete the Pont du Gard.

- A huge amount of rock went into its construction.

Over 21,000 cubic meters of rock

which weighed over 50,000 tons.

- [Narrator] Moving this huge volume

of material into position

would require a combination of ingenuity and muscle power.

[tools clanging]

- The Romans invented the Polyspaston crane

which allowed them to raise up immensely heavy stones.

- [Narrator] The key element of this crane

was a treadwheel in the center

that acted very much like a hamster wheel.

A crane operator would scamper around inside the device

to power its lifting mechanism.

A rope attached to a pulley was turned onto a spindle

by the rotation of a wheel,

allowing the device to hoist or lower the load.

In comparison, for the ancient Egyptians

it took a large number of men to haul

the 2.5 ton stone blocks

used to build the pyramids.

It's believed the Polyspaston crane

would be much more efficient,

as moving the same 2.5 ton block

would require just a small number of workers to lift it.

- Incredibly, human powered treadwheel cranes

remained in use until as recently as the 1900s.

[crane clicking]

[air whooshing]

[dramatic orchestral music]

- [Narrator] Once the Pont du Gard was finished,

an estimated 44 million gallons of water

float across it every day.

[water splashing]

[dramatic orchestral music continues]

And it has stood the test of time,

surviving some serious flooding over the last 2,000 years.

[water rushing]

[soft pulsing music]

One extreme event in September 2002 in Southern France

claimed the lives of 21 people

and caused millions of dollars of damage to towns

and villages along the River Gardon.

Over the past 10 years,

80 to 90% of all natural disasters worldwide

have been a result of floods, droughts,

tropical cyclones, heat waves, or severe storms.

Thanks to climate change,

floods are increasing in frequency and intensity

and may cause even greater damage in years to come.

- Cities and societies across the world

are having to come up with ever more ingenious ways

of coping with that danger.

- [Narrator] The solution may lie

with novel large-scale projects.

[air whooshing]

- London, for example, is very low-lying

and is seriously under threat from rising sea levels

on the one hand, and floods on the other.

- [Narrator] But fortunately, London is a place

where engineering has led the way.

In the early '80s, a barrier was built

on the city's Eastern boundary.

[pulsing electronic music]

It spans 1,700 feet, the entire width of the River Thames.

- The Thames barrier protects London from storm surges

coming from the North Sea into the Thames.

And essentially, it's made up of a series of gates.

- [Narrator] A total of 10 gates create a steel wall

protecting an area of around 50 square miles.

Each one is just under 66 feet tall,

weighs over 3,600 tons,

and can hold back a load of up to 9,000 tons.

[air whooshing]

Ordinarily, six of these gates rest on the riverbed,

but they're always on standby for a storm surge.

- If there's the danger that the river levels

are rising, then the gates rotate into position

and then stop the water from flooding into London.

[birds chirping]

- [Narrator] So far, the Thames barrier

has been raised nearly 200 times

in order to prevent flooding in Central London.

As well as finding ways of holding water back,

engineers have come up with spectacular ways

to keep water in.

Water is heavy.

Fill up an Olympic-size swimming pool,

[water splashing]

and you're talking about around 600,000 gallons,

making certain spectacular modern structures a challenge.

- When constructing swimming pools on top of buildings

there is no room for engineering structural errors.

- [Narrator] At the Marina Bay Sands Hotel in Singapore,

an infinity pool perches 55 stories up.

Supported across the top of three towers,

including the lookout decks,

it's longer than the Eiffel Tower laid on its side.

[soft upbeat music]

And at the Golden Nugget, Las Vegas,

is a 200,000 gallon shark-filled aquarium.

Fearless swimmers shoot down a three-story

enclosed water slide,

carrying them within inches of the sharks.

[water splashing]

[pulsing dramatic music]

Large pools are nothing new.

Public baths had been a feature of towns in ancient Greece,

but it was the Romans who went crazy for them.

Baths for washing and relaxing

were a common feature of Roman cities throughout the empire.

- Public baths were essential in cities

because the majority of people would not have had

bathrooms in their houses,

unless you were extremely wealthy.

- It was very much a communal enterprise

where all sections of society sat together.

- It was a duty almost

and it wasn't just about keeping yourselves clean.

This is where people went to discuss,

it's where politics happened,

it's where life was lived.

- [Narrator] At one point,

there were over 850 public baths in Rome alone.

Some of these complexes took on monumental proportions.

Feats of engineering built with vast colonnades,

wide-spanning arches, and spectacular domes.

The interiors were often sumptuous affairs

with fine mosaic floors, marble-covered walls,

and decorative statues.

[dramatic orchestral music]

Within the baths were separate rooms

containing pools at varying water temperatures.

The frigidarium, cold pool.

Tepidarium, for warm.

And caldarium, the hot pool.

- The Romans would start off in the tepidariums,

get ready for the caldarium.

And then, at the end of that bathing process,

you would go into the frigidarium

to close up your pores again

and get you ready for the outside.

- [Narrator] But how did engineers

control the temperature of the rooms and water?

[water splashing]

Early baths were heated with simple braziers

but from the 1st century BC,

a more sophisticated setup was deployed.

An innovative and complex system known as a hypocaust.

[soft dramatic music]

Furnaces attached to the bathhouses produced hot air.

This was fed below elevated floors

and up through hollow walls, warming the rooms.

Water was heated in boilers positioned above the furnaces

before being piped into the pools.

- Very early, very effective

form of central heating.

- But underneath all the glamor,

it would have been slaves feeding these furnaces

which was hard work.

[fire crackling]

- [Narrator] The baths of Caracalla

in the South of Rome are among the best preserved.

Constructed in the 3rd century,

their water came from the 57 mile long Aqua Marcia,

Rome's longest aqueduct.

Around 50 furnaces were needed to heat the complex.

The baths had four entrances

and could accommodate as many as 8,000 daily visitors.

As well as spas and pools, Caracalla had shops and eateries.

- They were the place you went to hang out,

to chat, to meet your friends,

to gossip, to see who's wearing what.

It was the place to see and be seen.

[soft relaxing music]

- [Narrator] Water may be vital for bathing

but it also plays a more hidden role in human hygiene.

As what goes in must come out.

- One of the interesting things about fresh water

is that on the one hand it provides life,

but on the other hand, it can be incredibly dangerous

if wastewater is not dealt with properly.

- [Narrator] It takes vast engineering infrastructure

to deal with the millions of tons of sewage

produced by large cities.

[water splashing]

The average human produces

over 320 pounds of excrement a year.

[toilets flushing]

- If we don't have proper sewage systems

to take this waste away,

then our cities and our settlements

become ridden with disease.

[upbeat electronic music]

- [Narrator] And water engineers now face a growing problem

in sewage systems across the world.

Fatbergs.

London, Belfast, Denver, and Melbourne

are just a few of the cities where these monstrosities

have been discovered in recent years.

[water splashing]

- Fatbergs are massive deposits of congealed fats

and other waste.

- [Narrator] New York City has spent $18 million

over five years on tackling them.

[upbeat electronic music continues]

And in one London sewer,

an 800-foot long fatberg was discovered,

weighing an estimated 130 tons,

the size of 11 double-decker buses.

- It's down to workers called flushers

to get rid of fatbergs.

- [Narrator] These fearless individuals

wear protective clothing and carry gas monitors

to ensure the air is safe to breathe.

They're tasked with manually breaking apart the fatberg,

aided by suction pumps and power jets.

[water splashing]

But blockages are a problem ass old as sewers themselves.

[soft upbeat music]

In ancient Rome, slaves were reportedly sent underground

to clear the drains.

And it seems the baths-obsessed Romans

may not have been quite as clean as previously thought.

- Roman cities would have been filthy.

And we think that Roman pavements in many cities

might've been built up very high

so that Romans walking around

didn't have to go anywhere near the gutters.

- [Narrator] Open drains were filled with waste

and raw sewage, causing an unimaginable stench.

But in the 6th century BC,

Rome's engineers came to the rescue

with a huge infrastructure project.

- The Cloaca Maxima, or the great drain,

was one of the earliest examples of Roman public sanitation.

- The Cloaca Maxima began as a type of open canal

but it developed into one of the most

complex sewerage systems in the ancient world.

- It was constructed as a stream which ran through the city,

draining the city of excess water.

- [Narrator] The Cloaca Maxima

originally measured over 320 feet long by 15 feet wide

and stood 11 feet high.

- The Romans realized that they had to cover it up

to protect the city from nasty smells.

- [Narrator] But this presented a major engineering problem.

The drain would have to be made waterproof.

[water splashing]

Roman engineers found a solution with a new type of concrete

containing lime and pozzolana.

[Volcano exploding]

Pozzolana derives from volcanic ash

and when combined with lime and water,

creates a strong concrete mix.

But the Romans also discovered

a unique advantage to their new formulation.

Unlike regular concrete, it could set in wet conditions.

- The resulting concrete that they made

could actually set underwater

and that was a really special feature.

- [Narrator] This technology meant that as Rome grew

so too could its sewage system.

The great sewer served the city for over 2,400 years.

And even today is still in use to carry stormwater away

into the river Tiber.

And Roman civil engineering projects

weren't limited to the capital.

- The Romans built them

in other parts of their empire as well

to make sure that those towns and cities

were well protected from pollution

and from the health issues that come with having

inadequate hygiene standards.

- [Narrator] Unfortunately, these improvements

didn't survive the fall of the empire.

[soft pulsing music]

Down the centuries, Roman advances in sanitation

were slowly forgotten.

[water splashing]

Only a few cities, including Paris,

preserved sections of their Roman sewage systems.

- What happens in the Middle Ages is that

in most cases these central systems of waste management

have broken down.

[footsteps crunching]

- The towns, the cities of Medieval Christendom

were the most revolting places.

It was a massive stinkpot.

[water splashing]

[footsteps splashing]

[soft pulsing music continues]

- Rats thrived among the excreta and epidemics of plague

and cholera broke out, killing millions of people,

about 25% of the Medieval European population.

[wheels clicking]

[air whooshing]

- [Narrator] But on a hilltop in the heart of Granada

in Southern Spain, engineers built a structure

that bucked this trend.

[soft ethereal music]

An oasis of cleanliness amid the general Medieval muck.

This 13th century palace was named the Alhambra.

- It's one of the great sites of Spain.

It's one of the moments where you can go

and stand and feel closest to Islamic Spain

and you can see just what a rich and vibrant

and exciting society that was.

- [Narrator] The Monarch, Mohammed ibn Alhamar,

at that time had a vision of transforming a dusty hilltop

into a lush oasis with a palace at its heart.

[water splashing]

So how was this dream made a reality?

[soft ethereal music continues]

First, engineers built a canal to carry water

from a river 3.5 miles up stream.

This was channeled into large reservoirs

on the hill above the Alhambra,

from where it flowed down through a series of channels

and pools to the palace.

- Inside the Alhambra is a complex network of channels

for the water to flow just using gravity.

- [Narrator] However, water supply

was seasonal and sporadic.

So a collection tower was used to make sure

there was always enough water for the gardens,

fountains, and baths, allowing the monarch's vision

to be realized all year round.

[water splashing]

- It was well-watered.

It was light.

It was dazzling.

It didn't smell.

It must have seemed to travelers like paradise on Earth.

- [Narrator] Just as ancient engineers

struggled to move water uphill

and transport it ever greater distances,

today it still remains a technological challenge.

[soft rock music]

Los Angeles, home to over 12 million people.

- There are an awful lot of people who want to live there

and that means that they need water

to support their irrigation,

their agriculture, their lives.

- [Narrator] Average daily water consumption in L.A.

is a colossal 131 gallons per person.

In such a dry part of California, essentially a desert,

where can so much water be found?

For years, Los Angeles relied on aqueducts

to transport water from rivers many miles away.

[soft rock music continues]

But as the metropolis grew,

engineers had to look further a field.

- In the 1960s construction began

on a new aqueduct system.

- [Narrator] This was infrastructure

on a totally different scale.

Stretching over 400 miles,

it would be the world's longest aqueduct.

Beginning just east of San Francisco

in the wetter north of the state,

the California Aqueduct

would wind its way south towards L.A.

But one major problem stood in the way.

[soft pulsing music]

- The engineers faced a significant challenge

at the end of the water's journey to get it to Los Angeles.

- [Narrator] The Tehachapi Mountains.

There were two choices.

Go through the mountain range or go over it.

Above ground seemed the cheaper and quicker option,

but how would engineers defy gravity

and move such enormous quantities of water uphill?

- Essentially, engineers had to build

one of the biggest water lifts

to get the water over the mountain.

- So to do this, they used enormous pumps

that had 80,000 horsepower.

- [Narrator] 14 pumps were installed

requiring around 60 megawatts of power,

enough electricity for a small city.

[soft pulsing music continues]

The aqueduct's main channel completed in 1973

supplies water to over 26 million people

and 3/4 of a million acres of agricultural land.

Today's engineers may have mastered

the art of controlling water,

but humans remain slaves to this vital resource.

And it's likely the world will face

ever more severe water shortages in the decades to come.

Already around one person in nine

lacks access to clean, affordable water.

And as the population grows, so too does demand.

It could be a catastrophe in the making.

- Finding and distributing fresh water

is continuing to be a big challenge to us

in the modern world.

- The 20th century saw war over oil.

The 21st century could very well be

the century in which we see war over water.

- [Narrator] But engineering solutions could be at hand.

- Distillation is a technology which is really important

for being able to provide fresh water.

Essentially turning salt water into fresh water.

- Desalination manages to make something deadly

into something that can bring life.

- [Narrator] Currently this method

requires a lot of energy, making it costly

while adding to global greenhouse gas emissions.

As ever, the world is looking to engineers

to find technological solutions,

ensuring the planet's taps continue to flow.

[soft dramatic music]

From the earliest tunnel systems in ancient Greece

to the simple tools that irrigated the Nile flood plains,

the water infrastructure that dominated the Roman landscape,

and intricate heating systems

that warmed their public baths.

Without the amazing innovations of ancient water engineers

disease and thirst may have held back

the development of civilization,

and the modern luxury of fresh water on demand

would not be possible.

[water splashing]

Thanks to engineers, safe and clean water

may one day be available for all.

[dramatic orchestral music]