Original subtitles

- [Narrator] The world's greatest structures,

push the boundaries of engineering,

all fueled by a constant desire to innovate.

- Without engineering, there would be no modern world.

- [Narrator] Gigantic buildings,

complex infrastructure and ingenious inventions.

- Engineering is the key that turns dreams into reality.

- [Narrator] Many of today's incredible achievements

rely on breakthrough technologies

first devised by ancient engineers.

- It's astounding how they achieved this.

- [Narrator] Early civilizations built

on an unimaginable scale and with incredible precision.

- They raised a bar for engineering

in a way that no one thought possible.

- [Narrator] These are some of the finest

engineers in history.

- [Narrator] Redefining the known laws of physics

and dreaming up the impossible.

They constructed engineering wonders

from colossal stadiums

to mighty waterways

and complex machines.

All with the simplest of tools.

- You cannot imagine the skills people

would've needed to build like this.

- [Narrator] By unearthing the mysteries

left by these ancient engineers,

we can now decode their secrets.

- That so many of their creations still survive

is testament to their engineering prowess.

- [Narrator] And ultimately reveal how their genius

laid the foundations for everything we build today.

(dramatic music)

From the very beginning, in all of its endeavors,

humankind has been willing to push the boundaries.

- Throughout the history of humankind

we've always wanted to go that step further,

higher, faster, deeper.

- [Narrator] The limits of what can be achieved

are only bounded by our imagination.

- Our ingenuity and our innovation has allowed us

to build some of the most extreme

engineering structures in the world.

- [Narrator] And extreme has meant

many things to many people.

- We might want to really defend ourselves strongly.

We might want to appeal to our gods,

but we might just build for the sheer heck

of impressing people.

- [Narrator] Humans have created

the most extraordinary feats of engineering

in the harshest terrains on earth.

From shifting desert sands to enormous sheets of ice.

But our desires to go to the extremes

can simply be to declare who we are.

- Sometimes we just build in an extreme way

because we like, as human beings,

to be the biggest and the best.

- This desire has been driven by a need to impress

the next generation, to make your mark on the Earth.

- [Narrator] Pushing the boundaries of engineering

is not a modern phenomenon.

It goes as far back as the ancient world.

At over 480 feet high and constructed of an estimated

2.3 million blocks of stone, the Great Pyramid of Giza

is one of the seven wonders of the ancient world,

but in the neighboring region of Mesopotamia,

another culture had developed a structure

on just as monumental a scale.

In what is now Iraq, Kuwait, Turkey and Syria,

between the great rivers of the Euphrates and the Tigris

lay the productive land of Mesopotamia.

Established by 5,000 BC.

It has become known as the Cradle of Civilization

because of the sophisticated cities which grew up here.

Some of them housing over 50,000 people.

- The ancient peoples of Mesopotamia

transformed the way that we see the world.

There you'll find the earliest evidence of writing.

They were mathematicians. They measured time.

They were surveyors

and they transferred all of those skills into engineering.

- [Narrator] The center of their universe was the king

who wielded power over his people

by claiming a unique connection with their gods.

These deities decided their fate

on every aspect of their lives.

But how could the king reach these gods?

- If you want to prove to your population

that you are close to the god,

you are the god's representative,

you want to go higher and higher and higher still.

In that sense,

they were literally building a stairway to heaven.

- [Narrator] The building that would bring power

and prestige to the king,

was a multi-tiered structure called a ziggurat,

meaning mountain peak.

And with some potentially reaching seven stories high,

they may have been the tallest manmade structures

on the planet at the time.

And the remains of these gigantic engineering earthworks

are still visible to this day.

One of these is the Ziggurat of Ur, built by one of the most

successful Mesopotamian Royals, King Ur-Nammu,

to the god Nanna in about 2100 BC.

- The Ziggurat of Ur, even with its remaining tier

is still an impressive feat of engineering.

It's something really amazing to behold.

- [Narrator] But the Mesopotamians had never seen,

let alone built, anything on this colossal scale before.

Did they have the brains and the brawn

to scale up their engineering?

- Up until this point,

they'd only ever built humble, basic structures.

So to then take their building to the monumental scale

of ziggurats, you can only imagine

the challenges they would've faced.

- [Narrator] The massive Ziggurat of Ur

was one solid wall of bricks.

210 by 150 feet around the base.

And up to three tiers with the base containing

as many as 720,000 bricks, soaring heavenwards.

It featured three huge staircases, one in the middle,

two others rising perpendicular to it.

Two massive buttresses prevented the weight of the building

thrusting the bricks outwards and causing it to collapse.

And its thought a shrine at the top was where the king

or priest made food offerings to their God.

The main component of their ziggurat

was something the people of Mesopotamia

had developed and used for thousands of years:

The humble mud brick.

- They made these bricks from clay and reed in a cast.

Bricks were cheap because they could be mass produced

using local materials.

So they were a very effective way

of building these structures.

- [Narrator] The challenge for these ancient engineers

was as monumental as the ziggurat itself.

As a building gets taller, the more important it becomes

to have solid foundations and precision building techniques.

As it grows, so does its self weight,

which all needs to be supported in the lower levels.

A small error near the bottom of the ziggurat

could lead to big problems at the top.

But to date, the Mesopotamians

had only tackled lower level dwellings.

- If you stack the bricks one on top of each other

in a straight line, you can only go so high

before you create an unstable structure.

- [Narrator] The Mesopotamian builders

had to think out of the mud brick box

to come up with a new method of arranging bricks.

- There are a number of things that the engineers could do

to make the structure last longer,

to make it stronger or more rigid.

They could fire the bricks

to make the bricks themselves stronger.

They could also lay the bricks as we would do,

in overlapping courses so that there is no single line

of weakness that runs right through the building.

The bricks help reinforce each other

and make the structure stronger.

- [Narrator] But there was another risk factor.

Situated on a huge floodplain,

flash flooding could see inches of rain falling

within hours, landing on the flat mud brick tiers

of the ziggurat.

- Now remember if you have an extreme weather event,

any building constructed out of mud bricks

is gonna be in danger.

It could turn to a pile of slush.

- [Narrator] To mitigate water damage on the bricks,

the builders took advantage of a material

that was in abundant supply in this part of the world.

Bitumen, a petroleum based substance

found in natural lakes in the region.

- Bitumen is a tar-like deposit.

It's sticky, black, very viscous, and also water resistant.

So it can be used to help glue the bricks together.

It gives them some structural strength.

It also helps waterproof the structure.

- [Narrator] But reducing water penetration

wasn't only about using cutting edge materials.

They engineered the entire ziggurat to include holes

at specific intervals between the bricks.

- The weeper holes that you see in the building

are actually gaps in between the bricks.

And they're there for a very functional reason,

which is to allow water to come out of these holes.

So with any building materials around the wall

and on the inside of the wall,

if you get any water pressure, hydrostatic pressure

building up there that could break the wall

if these holes didn't allow the release of that water.

- [Narrator] These mass construction projects

engaged every part of society

and were a constant reminder of the omnipresence

of their king and their god.

- When you think about something as complex as a ziggurat,

they are deeply impressive people.

And it's because they looked at the world around them

in ways that had never been done before.

- [Narrator] The Mesopotamian engineers

had not only created the most monumental structures

of this part of the world at the time,

but done it by refining the use of the brick,

a breakthrough in engineering

that would be used for millennia to come.

Today, they remain a key element in many types of modern

construction because of their inherent durability,

strength and ease of mass manufacture.

But a remarkable building built in 2014

has turned the humble brick on its head.

- It's a trick of the eye.

It's geometry is completely astonishing.

It defies logic.

It seems to defy even engineering.

And yet there it is, in front of you.

- [Narrator] The Dr. Chau Chak Wing Building in Sydney

was designed by famed architect, Frank Gehry,

whose work includes the much lauded Guggenheim in Bilbao

and the Walt Disney Concert Hall in Los Angeles.

Many of his designs feature complex geometry

and a fluidity of form, but this structure

is one of his most ambitious creations to date.

- This incredible squashed brown paper bag building,

called that because it looks exactly like that.

It's got crumples in it, bits that protruded out,

all these amazing geometrical shapes in there

that look like how could you build that

out of a solid material of brick?

- [Narrator] But this whole structure

is made from 320,000 of them.

To achieve this undulating shape,

Gehry threw out the rule book and digitally designed

five different bricks with grooves and unique shapes.

- To be able to work with these bricks

that were asymmetric and had different geometries in them

must have been so challenging.

It's something that no standard brick layer could do.

- [Narrator] These unconventional shapes

when placed together, create dramatically curved surfaces,

with some bricks sloping out from the wall

by up to 28 degrees.

Keeping them securely in place

presented a new set of challenges.

- The entire shell of the building was a steel frame

onto which they could then connect the bricks

using a specifically designed

bolt and groove brick tie system.

- [Narrator] A channel known as a frog

extends down the length of each brick.

The tie consisting of a threaded metal rod

with an adjustable square nut sits in this groove,

clamping it onto the brick,

securing the brick onto a steel stud frame,

which is covered with metal sheeting and a waterproof

membrane that follows the contours of the wall.

The tie can then be adjusted in and out

to match the curvature of the undulating facade.

- Then you could apply the mortar,

which meant that the ultimate end result

is that you get these beautiful geometric shapes.

This is really art meets engineering.

- [Narrator] The Dr. Chau Chak Wing Building

pushed the craft of bricklaying to its limits

and enabled the construction of a building

which makes a unique statement in its urban surroundings.

But the ancients also challenged

the accepted wisdom of construction techniques

when it came to extreme structures.

For thousands of years,

humans have pushed the boundaries

by engineering spaces deep beneath our feet,

like the rock hewn churches of Lalibela in Ethiopia,

carved in the 12th century out of one piece

of volcanic rock, making one of its 11 churches,

the largest monolithic place of worship on the planet.

But the engineering ingenuity required to create underground

earthworks like this goes back to prehistoric times.

And one of the most remarkable dates to 4,000 BC.

On the small island of Malta

is a network of underground alcoves and burial chambers

called the Hal Saflieni Hypogeum.

Believed to have been engineered by neolithic farmers.

- They would've had a very, very sophisticated

and complex understanding of the world around them,

but unlike us,

they would've had access to really quite primitive tools.

And that makes the cutting of these catacombs

all the more ingenious.

- [Narrator] With only basic implements,

they excavated a sophisticated labyrinth

of subterranean chambers completely by hand.

The Hypogeum's oldest and uppermost level

consisted of a central space

and an entrance to the lower levels.

The 13 to 20 foot deep middle level of 15 chambers

included the popularly known Oracle Room, an oblong chamber,

which created echoing acoustic effects

and the third lowest level at a depth of 33 feet

included five smaller burial chambers.

In this society, the dead and living coexisted

in the same sphere and the caves would've been used

for ritualistic ceremonies and burials year round.

- There wouldn't have been the fear of death

in the same way as we sometimes think of it today.

Death would've been very, very present

in these prehistoric times.

And as a result, people would've dealt with death

in a way that would've been part of the daily cycle.

(somber music)

- [Narrator] It's estimated up to 7,000 skeletons

could have been interred here

as part of their ritual burials.

But how could they carve out such deep chambers

for their dead and avoid cave-ins.

- In Malta there are regions of what's called coralline,

which is very soft material.

Building into this soft material

would've made it unstable and risk of caving in.

So part of the skill here was finding the right kind of rock

to excavate and build into.

- [Narrator] But these ancient engineers

knew their landscape well,

they chose an area of rock made from ancient fossils

called globigerina limestone, which carves easily,

but hardens on contact with air.

- The globigerina has this extraordinary quality.

Once you've carved it, there is a surface finish,

which gives it extra strength.

And therefore you can carve with enormous precision

and with certainty that the roof is not going to cave in.

- [Narrator] It's even more astounding to consider

they built these caves in darkness.

In recent times, experts have shed light

on a secret that has laid hidden for over 6,000 years

in the Oracle chamber.

- What they found was that if you made a really low pitched,

almost like a sort of chanting sound,

that that would resonate and echo throughout the chamber.

So what you've got here is some kind of primitive

sound system, creating that transcendent vibe.

- [Narrator] These ancient people

using the most rudimentary tools

had created caves of such strength and complexity,

they still defy belief.

while ancient humans moved heaven and earth

to build deep below ground,

in 37 BC, one man threw everything at building

a monumental structure in one of the highest,

most isolated places on Earth.

King Herod, known as Herod the Great,

ruled the ancient Roman province of Judea,

where Jesus would be born,

in the area now known as Israel.

This was a place of vast desert

flanked by the Dead Sea to the east

and the Mediterranean to the west.

But trouble was never far away.

- It was a real hotbed of local strife.

So to the south you had the Egyptians

and then all around you had other Jewish kingdoms,

all competing for dominance

where Herod wanted to base himself.

So therefore he needed to build somewhere

which was incredibly secure.

- [Narrator] To keep his enemies at bay, Herod turned

to a natural plateau that rose 1300 feet above the Dead Sea.

Measuring 1900 by 650 feet, it was called Masada.

- It's an astonishing place,

but very difficult to climb up to.

If you could make your way up there

and you could build fortifications,

it would seem to be impregnable.

So for security, it's a very good choice.

For practicality, maybe less so.

- [Narrator] Herod's vision was an entirely

self-sufficient fortress sustained by drinking water

which would be provided from giant cisterns,

holding runoff rainwater, and crops grown on the plateau.

He would have luxurious palaces

fit for a king of his stature.

And from this vantage point,

a bird's eye view of his enemies.

Engineering a fortress in such a remote location

would have its obstacles,

but Herod hit on one stroke of luck.

- There was a ready supply of dolomite rock,

which he was able to quarry and to do the quarrying

he actually had the assistance of some Roman soldiers.

It's worth remembering every single Roman soldier

was a trained engineer as well.

- [Narrator] To move the monumental stones

they had quarried on the plateau,

the Romans had a range of cranes in their arsenal,

including the greatest heavyweight of them all,

the tread wheel.

It was effective to lift huge stones

with the aid of another Roman invention,

the chain Lewis key.

It works by applying principles of the lever

and utilizing the weight of the stone itself.

A wedge shaped hole was carved

out of the stone to be lifted.

Two curved iron lever arms that swivel

were connected to a rope and lowered into the hole.

A crane lifts the rope and the weight of the stone

applies force to open the arms which make contact

with the stone inside the hole.

This outward pressure creates friction to prevent slipping,

allowing the stone to be lifted.

- With a Lewis key you can lift the stone,

move the stone, place the stone where you want it to go,

release the key and the job's done.

Beautiful and simple.

- [Narrator] After six years,

Herod's city on a hill was complete

with one of his palaces even appearing to hang off

the cliff face on natural steps.

- This was a place of gardens, of bathhouses,

of barracks and food stores.

This is an extreme example of fine living.

- [Narrator] To top it off, he erected the ultimate defense,

an almost one mile reinforced perimeter wall,

with 27 watch towers.

- By creating a place with resources for an army,

surrounded by a defensible wall on top of an inhospitable

plateau, he must have felt invincible.

- [Narrator] Dying in 4 BC,

Herod never had to defend his fortress,

but within 77 years, this siege-proof palace

would face one of the most dramatic attacks

in the ancient world.

From 66 AD, the Romans were engaged with putting down

a number of Jewish uprisings across Judea.

Meanwhile, one group of Jews took over

the small Roman garrison stationed at Masada,

where they managed to survive for several years.

- So the Romans have decided they can't allow

this outpost of what they would see as rebels to exist.

They've got to capture Masada.

- [Narrator] In 73 AD, 15,000 Roman soldiers

were sent to recapture it.

- The Romans arrive and they see that the rebel Jews

have encamped themselves in this tall plateau.

And so how are they gonna get even close to taking it back?

- [Narrator] They decided to build a giant ramp

from an existing outcrop of rock to take soldiers

and their battering ram to the front door of Masada.

Wooden boxes made of stakes and braces

were filled with stones, rubble, and soil.

They were stacked on top of each other,

starting with a few rising as the ramp

gradually increased in height to 300 feet.

And as the ramp fell short of the entrance to Masada,

they built foundations of closely fitted stones,

75 foot square on top of the ramp onto which they attached

a 90 foot iron tower from which they could launch missiles.

- So you imagine you're one of the Jewish defenders.

Now there they are at the bottom of the cliff face.

Every day this ramp is getting closer and closer

and there's absolutely nothing you can do about it.

- [Narrator] But as they reach the gates,

the Romans hadn't counted on the reinforced battlements,

which the Jews had built to resist the battering rams.

The Romans would need another ploy.

- So they used catapults to fire

flaming bolts into Masada itself.

And that started burning a lot of the buildings

inside Masada, but the wind was going the wrong way.

And therefore the flames blew back towards the Romans.

So it looked as though they may fail,

but then the fire took hold in Masada.

- [Narrator] The whole account of Masada

was recorded for posterity by Flavius Josephus,

a Jewish historian who lived at the time.

- Josephus says that the Romans eventually

successfully overcame the defenders

and they poured into the citadel expecting to find

the 900 or so enemies they'd been besieging up there.

- [Narrator] But what greeted them was silence.

As they entered, they realized the Jews were all dead.

- They found the Jewish defenders had committed suicide.

- [Narrator] Josephus gave an account

of what he believed occurred amongst the Jewish people

before the Romans entered Masada.

- The leader makes this great speech,

inspiring them to take their own lives.

And then they draw lots so that 10

of them will dispatch the others

so that they don't have the sin of suicide.

And then those 10 will kill each other

until there's a last man standing.

They had this pact to avoid falling into the hands

of their enemy because they knew what the Romans would do

if they caught them alive.

- [Narrator] In 1963, archeologists at Masada

made a remarkable discovery.

They unearthed stones with names written on them,

which they believe could be the lots

that were cast by the Jews.

Evidence which shows that while

one Roman feat of engineering protected the Jews,

another ultimately defeated them.

- We can say this was an extremely impressive

siege operation by the Romans, but ultimately a tragedy.

- [Narrator] Over the centuries different cultures

have also built death-defying structures

for defense, power or just because they could.

In ancient China in 491 AD,

a group of monks found one of the most unlikely places

on the planet to build a place of worship.

- This is the most precarious place to site a temple.

It looks crazy.

- [Narrator] The Hengshan Mountains in north central China

rise over 6,000 feet.

One of the mountain ranges considered sacred in China

for thousands of years.

The mountains were treacherous,

a place of snow and ice and the occasional earthquake.

But this didn't deter the monks

from building a sanctuary here for meditation.

- Building a temple in a gorge that has been created

by floods running through these two mountain sides

you'd think would be impossible.

However, these ingenious engineers

used what they had at their disposal

and built out of the sheer rock face.

- [Narrator] At a dizzying 295 feet above the valley floor,

about 30 stories up by today's standards,

the monks found their spot.

- This is not a building for the faint hearted,

even to visit, let alone build.

- [Narrator] The Hengshan Hanging Temples

would be a complex of 40 rooms and passages

dedicated to prayer and living

for Tao, Buddhist and Confucius monks.

But how could they affix a 10 ton temple

onto a sheer cliff face?

The first challenge was to get themselves, their materials

and equipment up the vertical mountain side.

- So if you are working with heavy wooden poles

and then you need to haul them onto the side of a cliff,

how do you do it?

- [Narrator] They decided to do something more akin

to modern rock climbing than ancient construction.

They would rappel off the cliff face

to get to their building site.

Without a flat foundation to work from,

they needed to engineer a structure that could be supported

from a sheer vertical cliff face.

A secured rope at the top of the cliff

allowed the monks to abseil down to a point

horizontal to where construction would begin.

A ledge was chiseled out of a natural groove

in the rock face, and a deep hole was cut into it

at the same level.

A fork was carved out of one end of a wooden beam

and a wedge inserted into the fork.

The pole was then pushed into the hole in the rock face

and on reaching the end,

the fork created outward pressure on the pole,

expanding it to secure it tightly in place.

This protruding beam acted as a cantilever

and was now stable enough for the workers to stand on.

Wooden materials could then be winched up

and this process was repeated horizontally

along the cliff face.

A platform was erected across the rows of poles.

So the structure could be built

and its entire weight safely supported.

Hundreds of years later, poles were added,

which seem to support the temples,

but these are all for show.

Against the odds, Hengshan has clung

to the sheer cliff face for 1500 years

through the incredible engineering skill

of Chinese monks hanging hooks in the sky.

- You have a sneaking feeling that these monks

might have needed to be spiritual to attempt this at all,.

'cause faith in God would probably be a useful thing.

- [Narrator] There is no greater challenge for engineers

than to build in evermore extreme conditions

than a previous generation.

And nowhere is there a better example

than in the national park Zhangjiajie

where engineers in modern China took a leaf out of the books

of the monks of Hengshan to build the world's tallest

outdoor elevator hanging from the cliffs.

- A huge pinnacle of rock.

How do you build an elevator up something like that?

Not to mention the accessibility of the site,

the Beilong Elevator is in a national park.

It's in the middle of nowhere.

- It's a daunting task.

You've got the elements to be aware of.

You're building out in the open,

let alone building something like an elevator

where you've got to safely transport people

from the bottom to the top.

This was daring engineering.

- [Narrator] The Beilong Elevator,

standing at over 1000 feet is embedded directly

into the cliff face and topped with a platform

which gives spectacular views of the surrounding mountains.

- The first thing that you've got to do is to make sure

that the materials you are working with

can actually withstand the immense pressures

that you're going to be putting on them.

- [Narrator] Engineers carefully chose

a very hard quartz sandstone cliff face

as the site to build the tunnels and shafts

they would need for their structure.

- So you've got the bottom part of the elevator

inside the rock face.

So that provides a nice strong base for you.

But then the top of the elevator

is on the outside of the mountain face.

So you've got this exposed steel frame,

supporting the lift as it goes up.

All these things that you have to factor in

when you're designing something that extreme.

- [Narrator] Secured to the cliff face,

three lifts can carry about 50 people at a time

with a total load of up to 10,800 pounds.

But amongst the serene beauty, danger lurks.

- It's built in an area renowned for earthquakes,

it would be absolutely terrifying if an earthquake hit,

this is a huge tall, narrow mountain, and it's gonna wobble.

You're a thousand feet up in the air.

You are crammed with people into an elevator

and then there's an earthquake coming.

What do you do?

- [Narrator] Engineers have fitted the elevator cars

with monitors to measure seismic activity,

which act as an early warning system

so it can be evacuated quickly.

- That is an essential piece of engineering.

- [Narrator] One of the fastest exterior passenger elevators

on Earth, it travels up to 15 feet per second.

- Would I ride in this lift?

As an engineer I'm intrigued.

If it's a brave day, I would.

- [Narrator] It's no wonder it's called

the Hundred Dragons Elevator.

You can get a ride on a structure as terrifying

as it's extreme, thanks to one of the most daring

engineering solutions on the planet today.

For the ancient engineers back in the fourth century BC,

no location could have been more ill suited

to sustaining a population than where the city of Petra

sits today in what is now Jordan.

- It's desert-like, it's very, very hot

and very dry indeed in the summer.

In the winter, it can get pretty cold

and there's also flash flooding.

So it's an unstable and hostile environment.

- [Narrator] But this area had one thing in its favor.

It sat at an important crossroads

supporting a trade taking incense, myrrh, silks,

and spices from the East to the West and back again.

- So this is an important trade route

and the Nabataeans are semi-nomadic people originally,

who participate in and help control these trade networks.

- [Narrator] It's this economic flow,

which provided a new opportunity for the Nabataeans

to put down roots.

- The money is flowing through the camel trains

and the trade routes, but capturing that money

and organizing it and using it to fund

the creation of a great city,

that's a real engineering challenge.

- [Narrator] The innovative engineering skills

required to establish the city

still amaze experts to this day.

Known as the Rose Red City,

famously hewn into the pink sandstone,

Petra stretches across 100 square miles.

Climbing high up sheer cliff faces,

it would've been home to up to 30,000 inhabitants.

But none of this would be possible

if they couldn't harness one vital natural resource.

- What's the one thing you need there

as this city begins to grow.

It's the need to store and control water.

- [Narrator] Could the Nabataeans turn an arid desert

using hydraulic technology

into one of the lushest oases of the ancient world?

- Their only chance to survive and thrive in the desert

was to harness the nearest significant spring.

And this is the spring at Ain Musa,

which is five miles away on high ground

above where Petra is.

- [Narrator] The problem was how to get it to Petra.

- You always have to manage the flow rates,

the hydraulic gradient of the water

so that it doesn't flow too fast, doesn't flow too slow,

just nicely in the middle zone, the Goldilocks zone.

So it perfectly supplies your city with what you need.

- [Narrator] They came up with one of the most complex

and audacious hydraulic systems in the ancient world.

Tens of thousands of one foot high fired ceramic pipes

were set at an angle sloping at exactly four degrees,

allowing the water to flow at just the right speed

from the spring to Petra.

But these ancient masters of hydrology

had further ways to optimize the flow.

Something which has only been revealed to us

over 2000 years later.

Recent research on shark skin has revealed

that it's rough texture actually reduces drag,

enabling sharks to swim at higher speed

than they would with a smoother skin.

Inspired by this work, researchers in industry

have found that just the right sized indentations

could reduce drag on the inside of gas pipelines,

the exterior of high speed trains, even golf balls.

And archeologists noticed something similar

hidden inside Petra's ancient water pipes.

- Essentially that the flow will be smoother

by five or 10% may seem counterintuitive,

but the ridges seem to help the water flow

smoothly along the pipe.

We don't know that the Nabataeans would've had any theory

about why this worked

like modern hydrological engineers would,

but by trial and error, they might well have found out

that pipes ridged in this way

produced a better flow of water.

- [Narrator] The water could potentially flow faster

and further, reaching more parts of the city.

As the population increased, pipelines

and open canals sprung up all over Petra,

but the unpredictable rainfall

threatened to cause supply issues.

- Water is such a precious commodity in the desert.

You have to be able to channel water, store it in cisterns,

keep those cisterns covered and cool

so the water doesn't all evaporate or stagnate

and to be able to draw on it in the summer when you need it.

- [Narrator] To better regulate the water output,

cisterns with giant sluice gates were built across the city

that could be lifted or closed on demand.

- They were almost like modern taps,

which you could turn off and on.

So if you have a caravan of traders and merchants coming in,

you increase the water supply, but then when they've gone,

you turn the tap off again.

It's water on demand.

- [Narrator] A massive hydrology network

of 125 miles of pipeline crisscrossed the city.

- They were going to palaces.

They were going to private homes.

They were going to gardens.

It was a hydraulic engineering paradise.

- [Narrator] Petra's hydro-engineering was unmatched

for another 2000 years,

but eventually after seaports became more important

and earthquakes damaged the city,

it was abandoned to the desert winds and lost in time.

With 95% of Petra yet to be excavated,

who knows what other marvels of engineering lie beneath.

But while the ancients harness

the natural water resources of the mountains,

today's engineers are using water

in a groundbreaking process, deep beneath the Earth.

After New York became an archdiocese in 1850,

the Archbishop of New York decided its Irish Catholic

population needed a large cathedral

to replace the old one in lower Manhattan.

- New York in the middle of the 19th century

was predominantly focused on the southern part

of Manhattan Island.

So what is today midtown Manhattan

was really quite a rural area.

- [Narrator] It was a project that some considered folly.

- To build such a big cathedral so far from the center

of New York life was a very bold decision indeed.

- [Narrator] The Archbishop's vision

was finally realized in 1879,

when the Gothic style St Patrick's Cathedral was opened.

- This was America's biggest Gothic cathedral,

and it would've towered above all other buildings

at the point at which it was built,

and for a community, a Catholic community

that was coming to America from Europe,

this was a beacon of hope.

- [Narrator] And the gamble paid off.

- If you build it, they will come.

And of course they did because midtown Manhattan now

is where we have Central Park,

the Empire State Building, Broadway.

- [Narrator] But churches and cathedrals

can be notoriously difficult to heat.

And in 2017 experts decided the whole building

needed an improved heating system,

but how could they update the cathedral without causing

havoc to the precious structure of the building?

- Changing any type of historic building

is fraught with difficulty

because there is so much protection around them,

but it's especially so for places of worship.

- [Narrator] Engineers turned to geothermal technology.

- Geothermal engineering is essentially using heat energy

in the earth to do work for us.

So we can use use that to thermally control buildings.

- [Narrator] This required engineers to devise

a radical design solution to access the geothermal energy

right beneath the cathedral.

10 wells each up to 2,200 feet deep,

six times the height of the spires,

were dug down to access groundwater located in aquifers

beneath the bedrock that remains at a stable temperature

of around 55 degrees Fahrenheit.

Two pipes connect each well to the geothermal plant.

In summer, one pipe sends this cooler groundwater

to a heat exchanger inside the plant,

which creates chilled water used to cool the air distributed

around the cathedral via coil fans and air handlers.

This same water now having absorbed the heat from the air

is sent back down via a second pipe

where the heat is transferred back into the bedrock.

In winter the reverse occurs as heat stored in the bedrock

becomes the heat source for the church.

This state of the art system

has saved up to 30% in energy costs.

- It's genius really, using geothermal energy

because if you're going to heat stone above the ground,

why not take that heat from the stone, the bedrock,

beneath the foundations of the building.

- [Narrator] While modern engineers

have found ways to harness nature,

ancient engineers sometimes had to vie

with the natural world.

And in ancient Sri Lanka, one team of engineers

used material engineering to overcome the challenges.

In sixth century India when the Buddha died,

according to myth, his ashes and relics

were deposited across the ancient world in stupas,

temples built to house his remains.

- This was to inspire awe.

It was to represent the grandeur

of the Buddha's spirit.

So these things,

they look like an entire world unto themselves.

- [Narrator] Shaped in a dome

to represent the burial mound of Buddha.

They rise from a wide base curving to a tiny peak

at their zenith, with a cavity

which would be filled with ancient reliquaries.

One of the most impressive stupas

built from 273 AD is Jetavanaramaya.

Soaring 400 feet high

with a footprint of 2.5 million square feet.

- This was the third biggest structure in the world.

Second only to two of the pyramids at Giza.

But what it's got over those pyramids

is that they are built of solid material.

This stupa is hollow.

And to do that is quite an amazing engineering feat.

- [Narrator] Building a structure on this scale

wouldn't be easy in the jungles of Sri Lanka,

a place where environmental forces

could destroy the very fabric of the building.

- One of the big challenges of building in the jungle

is that things like to grow there.

It's very moist and it's a constant warmth and sunshine.

So where the building meets the earth, plants want to grow.

Now the roots and the stems of plants

can destroy your structure over time.

- [Narrator] Recent research reveals

that it was these ancient engineers sophisticated knowledge

of the material world which allowed them to build

a stable structure in such extreme conditions.

- So what the builders of the stupa did was ingenious.

They had elephants to trample leaves down

that had been soaked in arsenic and sesame oil.

And the arsenic was essentially a weed killer.

So you're building on solid ground

ones that won't be undermined by plants.

- [Narrator] After filling the 28 foot foundation trench

with bricks and soil,

they could start to construct their dome.

Again, they turned to material science

Experts have found the bricks on the Jetavanaramaya

have a greater sand content than our modern day bricks,

making them much stronger and consequently able to tolerate

the vertical and horizontal forces of a dome.

And they applied even more material nous.

- By putting a slurry of fine sieved sand and clay together

between the bricks, they had this uniform glue between them

and they were clever enough to roughen

one side of the bricks as well so it had more purchase.

It gave the building more structural integrity.

- [Narrator] A mega structure that took 28 years to build,

requiring 93 million bricks,

Jetavanaramaya is the tallest stupa ever built.

- When we look at the nature of the materials they're using

and the way in which they're using them,

these are up there with the material scientists of today.

- [Narrator] These ancient people used their most

cutting edge technologies to overcome the challenges

of construction in adverse conditions.

And today modern engineers are still pushing the boundaries.

Now they're tackling the final frontier.

One of the most extreme environments in our universe.

- Lift off! We have a lift off!

- [Narrator] Space.

In 1998, a multinational group of designers and engineers

conceived and built the International Space Station.

Measuring 357 feet from end to end

and hurtling through space at 17,500 miles per hour,

it orbits the Earth so fast,

the crew witnesses 16 sunrises and sunsets every day.

But housing a team of astronauts safely in space

over long periods of time presents a plethora of challenges.

- How do you protect your astronauts

from the bombardment of radiation?

How do you provide them with enough oxygen to breathe?

And how do you power a space station sustainably

for years at a time.

- [Narrator] With an electrical power system

connected by eight miles of wire in a 446 ton structure,

where do you get your energy

without a power socket in sight?

- There's one thing that you've got a lot of up there

that we sometimes don't get enough of down here.

And that's the sun.

- [Narrator] Scientists and engineers developed a way

to harness the space solar power using solar arrays,

like our solar panels on Earth.

To launch them into space, engineers folded the arrays up

and deployed them remotely by signals

from the ground controllers once they got into orbit.

Containing over 262,000 solar cells,

these giant arrays are rotated on gimbals to face the sun

at the optimal angle to generate far more

than the station needs at any one time.

- It's almost inconceivable

that there's something manmade up in space,

something that's helping us understand the world,

the universe in which we live.

And it's all down to the most brilliant engineering.

- [Narrator] Today astronauts remain on board

for up to six months,

but in the future, the length of stay

could dramatically increase as humanity makes plans

to establish footholds elsewhere in the solar system.

As a result of findings on the International Space Station,

NASA's ambition is to set up a permanent base for humans

to live on the moon while private enterprise

dreams of establishing not only travel to Mars,

but a permanent base.

Humans have spent thousands of years

developing their engineering skills

to build structures in the depths of our planet,

at the extremes of temperature,

in the most challenging terrains

and have mostly succeeded against the odds.

So when it comes to the most extreme engineering

in the future, who's to say the sky is the limit.

(dramatic music)