Original subtitles

We are surrounded

by extraordinary feats of engineering,

constantly pushing the boundaries of what's possible.

Without engineering, there'd be no modern world.

Gigantic cities.

Amazing infrastructure.

And ingenious inventions.

Engineering is the key to turn dreams into reality.

To reach these dizzying heights

today's technology relies on breakthroughs

made by ancient engineers.

It's mind boggling how they did this.

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.

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.

Can you imagine the skills

people would have needed to build like this?

Now it's possible to unearth the secrets

of the first engineers.

They managed to construct edifices

that has survived the ravages of time.

And reveal how their genius

laid the foundations for everything we build today.

(awe-inspiring music)

Humanity is obsessed with surpassing

the limits of construction and engineering.

Establishing new records only to break them again and again.

As humans we always want to advance,

as engineers, always want to push the boundaries.

Every decade sees radical new structures.

And bigger is always better.

rising a dizzying half a mile above the desert,

Dubai's Burj Khalifa currently reigns

as the tallest structure in the world.

Wrapped in a glass curtain wall,

the supertower's sleek silhouette

dwarves the surrounding city.

And in Ontario, the Absolute Towers

appear to shimmer and twist around their own axes.

With continuous balconies and elliptical floor plans,

the skyscrapers take on shapes

that seem to defy the laws of physics,

But these architectural monuments also express the wealth

and power of those who commissioned them.

They are expensive and they're always symbols of power

to a certain extent.

Engineering as the ultimate status symbol.

They want to build the biggest thing they can do

to make a point of saying I was here.

Creating massive eye catching structures

is one of the best ways to impress.

Whether they're captivating onlookers

or symbolizing the might of a nation,

these statement buildings are found across the globe

reaching ever higher.

We certainly see it going on today,

the race to be the tallest building in the world.

But while modern tall buildings

are usurped by a new rival every few years,

in the ancient world, one civilization

built a structure that would reign supreme

for almost four millennia.

And it emerged in ancient Egypt.

In terms of building big, tall, structures

I don't think anyone rivaled the Egyptians.

What the Egyptians did was take monumental building

to its extremes.

Egypt's most iconic structure

became the tallest building in the world,

a title it retained for more than 3,500 years.

The Great Pyramid of Giza,

the largest pyramid ever built.

Last of the original

seven Wonders of the World still standing.

It was recognized by the ancient world as extraordinary,

and it's still an iconic symbol of Egypt

and of the ancient Egyptians today.

At a time when most buildings

were only one story high,

the Egyptians created something unimaginable.

Soaring to over 475 feet,

the pyramid remained the world's tallest structure

until the 14th century.

It's the biggest ancient building of them all,

it's still standing and it's a real icon.

But the great pyramid isn't only about scale.

With principles that still apply today,

it's also a masterpiece of mathematics

and precision engineering.

Aligned to face true north with pinpoint accuracy.

The size makes it impressive,

but it's also the dimensions, the proportionality.

The measurements are very accurate.

Each side is equal.

Built with over 2 million stone blocks.

Some seemed to weigh as much as two and a half tons.

And these fits together like a jigsaw puzzle.

The expertise that went

into making this thing was incredible.

It's a triumph against impossible odds.

Believed to have been constructed in just 20 years,

the result of extraordinary human ingenuity.

It's built in such a carefully engineered way

that it seems impermeable to the passage of time.

It's a solid structure built on solid foundations,

built to last, which indeed it has.

The great pyramid

is an ancient engineering masterpiece,

but this world famous monument is still shrouded in mystery.

For centuries it has remained

one of the great engineering enigmas.

The complex engineering that went into that

without the modern day technology

that we have is really astounding.

The kind of challenges just to build something of that scale

with the materials they had available

is really an amazing feat of engineering.

What drove the Egyptians

to erect such enduring monuments in the first place?

Of course, there are many theories

as to why the pyramids were

constructed by the ancient Egyptians.

Were they really enormous burial places

with hidden chambers inside?

Or did they serve another function?

Even the ancient Egyptians looked back generations later

at this thing, with some degree of mystery.

To find answers, we need to go back

to the first pyramids.

Over 5,000 years ago,

Egyptian civilization began to emerge

along the banks of one of the world's longest rivers,

the Nile.

For the ancient Egyptians

the Nile was fundamental to their entire culture.

Without the Nile there is no Egypt.

Annual floods brought nutrient rich waters

to the lands along the Nile's banks,

giving life and fertility.

It's that that could support this great civilization

and allow it to store grain and grow and grow and grow

and do more and more remarkable things.

For the most part, it was a blessing

and Egypt became a land of plenty,

but during times of drought, there was starvation and death.

If the Nile flood was too low, then famine would follow.

If the Nile flood was too high,

then entire villages could be washed away.

This precarious existence

led to an obsession with death and the afterlife.

And in order to protect the bodies of their dead,

the Egyptians developed a method of artificial preservation,

mummification.

Mummification was invented to provide

a permanent physical home for the soul,

which could wander around, live forever

and then come back at will into its body.

The body of the deceased

was washed and purified.

All the organs were removed, excluding the heart.

It was then dried out with salts

and wrapped head to toe

before finally being laid to rest.

Some bodies were simply wrapped in linen

and put in the desert.

The desert sands may have been good enough

for ordinary Egyptians,

but they're mummified rulers

demanded a more secure resting place.

The ancient Egyptian king was essentially worshiped

as a kind of god in life,

and certainly as a god in the afterlife.

Workers used simple hand tools,

excavating huge underground burial chambers for their kings,

protective tombs for their journey into the afterlife.

And mummification continued for thousands of years,

but other techniques for preserving

the human body after death have since been invented,

including one very recent innovation.

Hundreds worldwide have had their corpses frozen

in special cryogenic chambers,

preserving their remains in the hope that resurrection

may be possible in the future.

People hope that when they're eventually

brought back to life,

that there will have been advances in medicine

that means there'll be able to treat incurable diseases

that we have today.

The procedure must begin minutes after death.

Antifreeze compounds replace the corpse's blood

to prevent harmful ice crystals forming

as the body is slowly cooled to a temperature

of minus 320 degrees Fahrenheit,

and finally lowered into a tank of liquid nitrogen

where it remains ready for the afterlife.

But over 4,000 years ago,

all the ancient Egyptians had was their belief in the king.

And they were certain the efforts their engineers made

to preserve the royal body would be rewarded.

Each royal mummy had to be buried

in a very, very safe place.

And it was only when this was done

could Egypt truly thrive because it was believed

that each successive Pharaoh contained divine power.

By creating a secure burial chamber for the King,

the people believed that the survival

of their civilization was insured.

So royal grave sites became unmissable monuments.

The earliest Kings were buried in

what we call mastaba tombs,

low rectangular structures with sloping sides.

They can be quite large, but they weren't made from stone.

These were made from mud brick,

Mud brick was the most common building material in Egypt

because simply it's made of the mud

from the banks of the Nile.

But a belief in the afterlife,

wasn't the only motivation for tomb building.

Each successive ruler wanted

a memorial larger and grander than the last.

Royal tombs had become a mark of status.

Then around 2650 BC,

one genius of ancient engineering had an outlandish,

world-changing idea to take tomb building to new heights.

King Djoser had his architect Imhotep

embellish his simple mastaba tomb.

You can see the really big leap from the previous phase.

This huge leap that Imhotep seems to make.

One that would change

the Egyptian landscape forever.

Imhotep wanted something grander to commemorate his king

and took Egyptian engineering to the next level, literally.

He envisioned six different layers of mastaba

stacked on top of each other,

but this new design would involve a tremendous amount

of material and weight.

So a radical breakthrough was needed.

The great leap forward

was that the Djoser's pyramid

was built of limestone rather than mud brick.

The use of stone revolutionized construction in Egypt.

The architect Imhotep also changed the design,

instead of the rectangular mastaba,

it was made into a square,

which is effectively far more stable.

Imhotep had designed Egypt's first pyramid.

It would prove a massive undertaking.

Building with stone is not easy.

It's not cheap, it takes a long time.

It's not an easy material to work with.

Over the course

of Djoser's nearly 20-year reign.

His builders assembled the six stone layers of his pyramid,

a colossal structure,

unlike anything the Egyptians had ever laid eyes on.

Djoser's pyramid is probably

the world's first monumental building in stone.

This engineering masterpiece reinforced

the king status as a living god.

196 feet tall, the groundbreaking form

would come to be known as a step pyramid.

It can only be imagined

what impact first pyramid must have had

on the Egyptian population.

The whole structure was designed

to be seen from the valley below.

Imhotep would go down in history

as the world's first engineer and architect known by name.

He had created the original skyscraper.

Some modern architects have also become household names,

world famous, thanks to their unique designs.

One of the greatest in their ranks is Frank Gehry.

His buildings are monumental works of art.

He has such a signature style to him

that you can pretty much look at a building

and probably guess correctly that that that's a Gehry.

Cutting edge technology

helps deliver the engineering solutions

that bring Gehry's sculptural sketches to life.

For me it's about his use of geometry

to create really, really unusual shapes.

In a sense he was a bit like the Egyptians

who built the pyramids as they were making things

that would make people go, wow, look at that.

New forms never seen before.

Making headlines around the world.

Gehry is an architect who refuses to accept limits,

something he and Imhotep appear to have in common.

But why was the step pyramid design

chosen for Djoser's tomb?

Some believe that the pyramid sides

act as a celestial staircase,

guiding the Pharaoh's soul to the afterlife.

Or could Imhotep have had a more practical reason?

If one looks at the grains of sand

trickling through an hourglass,

they naturally form a pyramidal shape.

And that's because the pyramid is a deeply stable structure.

And a stable structure is a strong structure.

A pyramid is very stable because of having a large base

compared to its height.

You've got basically a very low center of gravity.

It's a structure that as long as you expand the base

can grow infinitely large because the base

will sustain the structure as far as you want.

Their stable form explains

why the pyramids of Egypt are still standing tall,

enduring weather and erosion over millennia.

Djoser's step pyramid launched an engineering arms race

that would continue for centuries.

After Djoser, the pyramid became

the kind of stereotypical monument

in which a king would be buried.

They were really showing off the might and power

of the Egyptian empire at the time.

We do the same thing today.

People build taller and taller.

But as with everything in the modern world,

even big buildings need to be put up as quickly as possible.

In New York city,

marvels of engineering continue to be developed.

High profile skyscrapers,

many of which reach 1000 feet tall

with more and more commissioned each year,

the scale of this new wave of construction is unprecedented.

And thanks to modern materials and techniques,

each building can be completed within a few years.

In ancient Egypt

pyramids couldn't possibly be built this fast,

but the pressure was on.

Not only to be ready for the death of the Pharaoh,

but to go taller than before.

There was this real desire

to exceed what your predecessor had done.

There is a kind of mark of your status, of your ability.

Pushing pyramid construction to the next level

called for new architectural and engineering skills.

Djoser's successors must have seen Djoser

as a very hard act to follow.

Most of them had very short reigns

and of course you can't achieve much

if you're only on the throne for two or three years.

In fact, for the next several decades,

not a single pyramid was built successfully

until one Pharaoh changed ancient engineering forever.

In the fourth dynasty of ancient Egypt,

King Sneferu was determined to build a pyramid

far larger than his predecessors.

Blinded by ambition, his monument was destined

to meet with terrible disaster.

Sneferu began constructing the pyramid of Meidum,

a step pyramid similar in design to the original,

but significantly taller.

But halfway through construction,

the step design was mysteriously abandoned.

It seems that the king had a desire to smooth the sides,

to create a true pyramid.

The King asked that his workers fill in the steps

with limestone and then apply smooth casing to the outside.

It was a revolutionary concept,

but something went terribly wrong.

Modern archeology has revealed

that the outer layer of limestone rested on sand

rather than solid rock.

It put the basis of the four external supporting walls

under enormous pressure.

Something had to give.

Unfortunately at some point, probably during construction,

these sides began to crumble away.

As if an anticipation of defeat,

the king had already begun construction on his next pyramid.

It's a much larger construction than the previous pyramid.

And that's going to come with a whole bunch of challenges.

But as his new pyramid grew skyward,

Sneferu found himself once again,

on the brink of disaster and construction ground to a halt.

They might have thought that the amount of stone

that was gonna be needed to complete this thing

and the height that it was gonna to get to

was just gonna be too much.

Without a drastic design change

the pyramid couldn't be completed.

Determined not to disappoint their king,

Sneferu's engineers changed the angle of the upper section

from the original 54 degrees to a much shallower 43,

a modification that would significantly reduce the volume

and weight of the pyramids upper half.

The compromise worked, but it came at a cost.

In saving the structure, the engineers produced

the strange, comical shape in evidence today.

It's gone down in history as the bent pyramid.

Last minute modifications

are still commonplace in construction.

Most are only minor,

though there are exceptions.

In 1971, the John Hancock tower in Boston

was mid-construction when something unexpected happened.

(glass cracks)

Glass began smashing onto the streets below.

(people shout)

To the engineer's horror,

the reflective windows were falling out of the building.

There was too much movement taking place.

And so the stresses in the glass

were causing these windows to break

and actually pop out of the building.

Over 10,000 window panes

had to be replaced with heat-treated panels.

This new glass had to be processed through a furnace

to significantly increase its strength,

providing greater resistance to thermal

and mechanical stresses.

But replacing the old windows was a long and costly process.

This is one of the challenges

of these prominent buildings.

They're in the public eye as they're being constructed.

And so any mistakes that happen

are very public and very embarrassing.

Before the new panels could be installed,

the empty frames were covered up with sheets of plywood,

earning the tower the nickname, Plywood Palace.

Errors like this are hard to ignore.

And despite reaching over 220 feet tall,

Sneferu appears to have seen his bent pyramid as a failure,

but the King and his engineers learned from their mistakes

and moved on to a third attempt.

They now knew that large high-quality blocks of limestone

would strengthen a pyramid's foundation

and a wider base with a shallower angle of incline

would increase its stability.

It is 43 degrees,

like the top part of the bent pyramid from the base.

So it's a very low lying period.

After decades long attempts,

Sneferu had finally achieved the perfect pyramid form.

Engineering genius had triumphed against all odds,

creating the first success of a new breed,

the Red Pyramid.

It's what you call a perfect pyramid.

The one that conforms

to what we think of as a pyramid the most.

The smooth and symmetrical shape

recognized worldwide.

And at 229 feet tall Sneferu's monument

would be a tough act to follow.

But this remarkable structure

didn't Mark the Zenith of pyramid building.

Sneferu's son, Khufu would in turn dream the unimaginable,

determined to be remembered

as one of Egypt's greatest rulers.

In the 26th century BC,

one of his first decisions as Pharaoh

was to commission his own grand tomb.

This was intended to be a new pyramid

on a totally different scale.

There was an element of wanting

to build bigger and better than his father.

It was down to him to excel the king that went before.

Could it even be done?

Planned to cover an area more than 12 acres,

Khufu's pyramid would require

more than 2 million stone blocks to complete,

adding up to a total of six and a half million tons.

More than 17 times the weight of the Empire State Building.

And accuracy of form and measurement

were of paramount importance to Khufu's architects.

One small error at the base

would lead to a complete disaster closer up to the top,

so the alignment and accuracy

of placing every single block as they went was critical.

Creating such a monumental masterpiece

would demand tens of thousands of workers.

But would Khufu's great pyramid

be built by an army of slaves or willing laborers?

For years, controversy raged.

Then in 2010, mud brick tombs

were discovered near the great pyramid

more than 4,000 years old.

These shafts contain the skeletons of pyramid builders,

well-preserved by the dry sand,

along with clues to how the workers were treated in life.

They were provided with food for the next world.

They were provided with the cans of beer and bread

that they'd enjoyed in this world.

And some of the tombs even have inscriptions on them

telling us who was buried inside, what job they did.

The tombs provide strong evidence

that the great pyramid was built

by skilled construction workers,

highly regarded for their craft,

not a disposable workforce of slaves.

They may have been willing workers,

but a monumental job still lay ahead.

To build something like the pyramids,

you've got to organize the movements

of massive amounts of material

then creation of the blocks that you need.

Cutting the rock would be a Herculean task

for laborers equipped only

with copper chisels and crude hammers.

The sheer physicality of this kind of work.

The physical toll that must take on the body

would have been immense.

Theory suggests that

up to 20,000 workers toiled on the great pyramid,

consuming vast quantities of raw materials.

Since Khufu's reign, demand for natural resources

has grown exponentially.

Quarrying now takes place on an industrial scale.

Reaching far deeper than

the Egyptians ever imagined possible.

Modern day quarries and mines are enormous undertakings

compared to ancient predecessors.

Two and a half miles wide

and three quarters of a mile deep,

Bingham Canyon outside Salt Lake City

is considered the largest mine on Earth.

It's also one of the most productive.

As of 2018 Bingham Canyon generated

approximately 19 million tons of copper,

more than any other mine in history.

The sort of machinery that's used on them

is pretty terrifying, actually awe-inspiring.

Bucket wheel excavators,

capable of moving millions of cubic feet every day,

equivalent to more than 20,000 fully loaded dump trucks.

We might go and doff our cap to the Egyptians

for their pyramids.

If they were see our quarries and our mines,

they would doff their caps in return.

Mining was a much slower business

in ancient Egypt.

Even once stone had been extracted,

another great challenge remained.

Transporting it to the build site.

A recent discovery has revealed exactly how it was done.

In 2013, a team of archeologists

came across something remarkable,

hundreds of miles from the pyramid side at Giza.

Dozens of inscribed papyrus fragments,

written more than 4,500 years ago during the reign of Khufu.

These are essentially a logbook.

What they tell is that foreman called Merer,

and he's commanding a ship,

ferrying goods from one part of Egypt,

all the way up to the Giza Necropolis

where the pyramids are built.

Merer recorded his daily activity,

transporting stone by boat

from the Tura Limestone Quarry to Giza,

ferrying blocks from this quarry,

and others along the Nile

ensured enough stone reached the pyramid site.

All thanks to a mode of transport

on which the modern world still depends.

Cargo ships carry billions of tons of goods

across the globe each year.

And that number continues to rise.

We've become very used

to the idea of containerized transport,

and it affects how we move stuff around the world.

Container ships

reach up to 1300 feet in length,

capable of carrying over 100,000 tons in a single journey.

Thanks to their shipping skills,

the ancient Egyptians maintained a steady supply of blocks

to the pyramid site.

But the biggest challenge still lay ahead.

How do you get that block that you've quarried

and put next to the pyramid up into the pyramid itself?

One recent idea may explain

this long-standing mystery.

Many Egyptologists suspect that ramps were used.

It's likely engineers used

a large single ramp leading to the pyramid.

And the ancients knew it was crucial to get its angle right.

Anything beyond six or seven degrees

becomes very, very difficult

to then push a large block uphill.

But keeping the ramp shallow

would force it to cover a huge distance.

It would be miles long to get to the top of the pyramid.

So it would take longer to build a ramp

than it would take to build a pyramid.

That doesn't make any sense.

Speculation continues

as to exactly how the Egyptians built their giant monuments.

Pyramids are so extraordinary

that people have always struggled to believe

that they could possibly have been built

as long ago as they were.

And their perfection

has become a breeding ground for wild theories

with some suggesting that there's something else going on.

People when faced by the pyramids,

look at this and think it can't possibly have been done

without some force from outside.

Did this ancient civilization

have alien assistance?

That couldn't possibly be true.

The arguments are fabulously speculative,

none of them plausible, none of them real.

I feel quite offended on behalf of the ancient Egyptians

that their abilities are called into question like this.

Of course, the Egyptians built the pyramids.

They did so brilliantly.

There may be precious little evidence

to support how the pyramids were built,

but there's no doubt that these mighty tombs

were constructed by skilled Egyptian craftsmen

without any outside help.

Certainly not from aliens.

And the Egyptians engineering brilliance

didn't stop at the pyramid's limestone exterior.

The great pyramid isn't a completely solid structure.

There are chambers and pathways within it.

A grand tomb for the king,

with the king's chamber right at the pyramid's heart.

Today, all that remains

is Khufu's giant granite sarcophagus

along with two tiny shafts on the north and south walls.

Originally, it was believed that

these could be air shafts for the burial chamber,

but that seems unlikely.

Then in 1964,

astronomers made an extraordinary discovery.

One shaft aligns precisely with Orion's belt

while the other lines up with the North Star,

as it would have appeared in ancient Egypt's night sky,

both shafts rise at constant angles,

each running for more than 130 feet

through the body of the pyramid.

They are intended to provide a clear sight line

from the burial chamber up to the stars.

An engineering phenomenon,

all to guide the king's spirit after death.

There's a desire for the royal soul

to emerge from the mummified body

and ascend to not only the gods,

but also to travel up into the night sky

and join with the stars.

Launch pads to the afterlife.

But the Pharaoh wouldn't ascend to the heavens empty-handed.

Egyptian rulers were often buried

with their most prized possessions

to accompany them in death.

Gold, silver, and bronze artifacts

were loaded into their great tombs

while fine linens and artwork adorned the secret chambers.

All the things that made yourself happy here and now.

So you could carry it with you into the world beyond.

But this wasn't simply about jewels or gold.

Egypt's greatest treasure was the mummified body

of the god king, which must be protected at all cost.

The burial chamber itself is quite incredible.

It almost looks like a bank vault.

Egyptian engineers are thought to have used

a 3D scale model of the burial chamber,

a surprisingly modern technique for construction.

If you were thinking about designing something

like a pyramid today, we would be designing that digitally.

So we'd have a 3D digital model

to understand what the space was like inside.

No expense was spared

in designing the king's burial chamber.

Engineers devised a way to plug the passages with stone,

sealing off the tomb,

securing the site where their king's journey

into the afterlife would begin.

In 2560 BC, after two decades of work,

the great pyramid of Giza was completed.

Khufu had created a symbol of his absolute rule,

towering 479 feet over the Egyptian desert.

To see this, the biggest structure

anyone had ever seen in all human history.

I mean, it's hard to imagine what it must've been like.

Armed with basic tools and clever engineering

the ancient Egyptians had created a structural marvel.

It's staggering to think for almost 4,000 years.

The great pyramid of Giza was the tallest building on Earth.

An eternal testament

to the power of their empire.

This is a statement piece,

the wealth, the might, the power

and how important this person is.

Originally covered

by a smooth sloping of fine, white limestone

the monument was once even more striking,

gleaming in the sunlight.

The last of the seven wonders

of the ancient world to survive.

It's one of the most well-studied buildings on Earth,

but there's still so much left to learn.

In many ways we've just scratched the surface

and the more rapidly modern technology develops,

the more we're finding out about ancient Egypt.

Often a discovery

raises more questions than it answers.

In 2017 scientists detected

a previously unknown void within the structure.

Techniques including thermal imaging

helped identify a space roughly 98 feet long

above the giant passageway

leading to the king's chamber.

It gets people really excited

and people think there's another chamber.

This could be where someone's buried and where goods are.

But it's true purpose remains a mystery.

Despite archeologists best efforts,

the great pyramid retains many of its deepest secrets.

And it's just one of many pyramids yet to be fully explored.

The ancient Egyptians went on to build

more than 80 further pyramids across the country.

But none surpassed the magnitude of Khufu's great pyramid.

Over the centuries,

the scale and precision of construction tailed off.

They're not being built in the same way

as those earlier pyramids.

And what happens is these things

don't stand the test of time.

But why did

Egypt's pyramid building craze die out?

Tomb raiders were a massive problem for the Egyptians.

People who were well aware of what was within those tombs.

Of course, it doesn't take a genius

to work out where that goal might be.

You might as well just put a big cross.

Eventually, the Pharaohs

were forced to change their approach to royal burials.

A thousand years after the great pyramid age,

the pharaohs of the new kingdom established

a secret burial place on the Nile's west bank,

the Valley of the Kings.

More than 60 tombs were carved across this remote valley.

The Valley of the Kings contains burials,

which are cut directly into the rock itself.

Including the most famous

Egyptian burial of them all,

the boy king, Tutankhamun.

Today, engineers have dug one structure deep underground.

Not to protect a king,

but to ensure the continued survival of nature itself.

Deep in the bowels of an icy mountain

on the Island of Spitsbergen

lies the Svalbard Global Seed Vault,

a secure facility where more than a million seeds

from the world's agricultural plants are kept.

Constructed in 2008,

the site was chosen for its position below permafrost

and thick rock over 320 feet within the mountain

where the seed samples will remain frozen

even if the power supply fails.

It's a gigantic safety deposit box,

which holds the world's largest collection

of agricultural biodiversity.

The facility ensures

that biodiverse plant life could be restored

after a great natural disaster or global catastrophe.

And as ancient Egypt's rulers continued

to be buried away from prying eyes.

The pyramids were soon forgotten.

But elsewhere their story was only just beginning.

In a burst of creativity around the eighth century BC,

one of Egypt's neighboring kingdoms

began their own pyramid building craze.

Few people realize there are more than twice

as many pyramids over the Southern border

in ancient Nubia, modern Sudan.

But Sudan's pyramids

would be radically different.

Their angle of incline is far, far steeper

than the Egyptian ones.

And more often than not, they are considerably smaller.

For visitors these ancient structures

are striking sites to behold,

the last pyramids of ancient Africa,

but on the far side of the world, other empires were rising.

From around 1200 BC,

advanced societies emerged in the Americas,

the Olmec, Maya, and Aztecs flourished across the region

developing great civilizations up until the 16th century.

And they had one thing in common.

Pyramids.

These civilizations began constructing

the sky high structures at a remarkable rate.

We can literally say that thousands of pyramids

dotted the Mesoamerican landscape.

More pyramids than

in the rest of the world combined.

Topped with elaborate platforms

they became the glorious centerpieces

to vast ancient cities.

Believed to house their deities

and serve as tombs for their dead kings.

But was that the entire story?

Do these mighty structures conceal a dark and bloody past?

Once the most populous city in the Americas,

Teotihuacan sprawled over an area larger than ancient Rome.

Teotihuacan was a very large city,

possibly having a hundred thousand inhabitants at the peak.

The largest city

anywhere in the western hemisphere.

Yet little is known about the people who lived there.

Teotihuacan is a major site.

It was prominent until about 600

and then things began to decline.

The city was suddenly abandoned

and it's still not clear why it's people

and their culture vanished overnight.

We have several signs of destruction.

Monuments were destroyed, the city was burned.

Now the pyramids and ruins

are all that remain of this once majestic city.

And they offer insight into the lives

of the Teotihuacan people.

But there have also been some disturbing discoveries.

Beneath one of the city's largest structures

known as the Pyramid of the Moon.

Archeologists were shocked by what they found.

Underground chambers filled with animal and human remains,

including human skulls.

The ritual activity of the temples

sometimes entailed the participation of human beings

that were offered up ritually,

individuals that were killed ritually.

Some were captives of war.

We know that they had their hands tied up.

Large offerings, including human sacrifices

were made regularly in an attempt to appease the gods.

Some even believed that it would prevent the apocalypse.

Despite their bloody and brutal history,

these monuments are marvels of the ancient world,

still standing centuries

after their creators all but disappeared.

Pyramids are among the most enduring icons

of the ancient world.

Even today, they feature heavily in architectural design.

Modern architects still find that shape fascinating,

it's perfection, it's symmetry,

the way that it connects us back to our history.

And you see that now reflected

in buildings around the world.

The Luxor Las Vegas Pyramid

is specifically modeled on Khufu's grand tomb,

complete with its own Sphinx and obelisk.

And in Paris, the glass pyramid fronting the Louvre Museum

is one of the city's most notable landmarks.

That pyramid shape is still something that we desire.

I think there's something about the symmetry

we seem to have an affinity or a liking to.

Pyramids are part of our common global culture.

Even found on the U.S. dollar bill,

a homage to Egyptian ancestry in updated form.

Dating back more than 4,500 years,

pyramids revolutionized construction in the ancient world.

They consumed materials and labor on an unparalleled scale,

requiring engineering know-how never seen before.

Today they continue to inspire.

And it doesn't look like these iconic structures

will be going anywhere soon.

The pyramid, an ancient design so perfect

it has survived the ages.

(epic music)