Ancient China from Above

allan: It's tiring, the winds blowing, its icy cold.

This is so steep I don't know how they got the bricks up here.

The great wall of china.

Wow!

It's like being on the top of the world.

Endless wall, endless watchtowers all the way to the horizon.

It's like nothing you could ever imagine.

It's been studied for decades, but now new technology

is revealing its secrets like never before.

I'm allan maca.

An archaeologist and expert in ancient civilizations.

And I'm going to investigate china's distant past

from a whole new perspective, space!

Today, state of the art satellites see the world in stunning detail,

and reveal hidden archaeology.

Enabling us to recreate a lost ancient world,

invisible to the naked eye.

Working alongside leading chinese experts,

my team and I will travel to some of the country's

most remote and incredible landscapes,

and with cutting edge science, investigate previously unknown

cultures, lost cities and devastating cataclysms.

This is ancient china as you've never seen it before.

Just outside china's capital beijing,

10 million people a year come to marvel at the great wall.

This is the biggest manmade structure on the planet.

But the only way to really see just how vast it is,

is from 500 miles above the earth.

Using satellite images, I'm going to track the great wall

across towering mountains and remote desert.

Exploring massive defenses.

They would just start raining down fire and arrows from above.

Meeting archaeologists as they unearth its ancient past.

Wow, this is amazing you've literally just found these.

And revealing its long hidden secrets...

Sarah: This looks really cool.

Allan: To discover if this great monument could be

even bigger and far older than we'd ever thought before.

I'm starting my mission 70 miles north of beijing in the

rugged mountains of jinshanling.

At a part of the wall that's remained unchanged

for hundreds of years.

You see pictures of the great wall in tourist books,

but this is something else.

Out here in jinshanling, satellite data shows

how the wall crosses seemingly impossible peaks.

And every few hundred feet,

huge stone structures.

On the ground, these towers reveal meticulous engineering.

Look at how beautiful this is.

Really formal arches here, lots of space,

windows all the way around.

You have a 360 degree view over the landscape.

It's incredible.

This is just one of around 25,000 watchtowers

built by the ming dynasty,

who ruled china from 1368 to 1644.

Between the towers, ingenious defenses.

I'm seeing these strange holes along the wall

that open to the outside.

What they would have done is they would have taken about a

five-pound rock, hollowed it out,

stuffed it with gunpowder, put a wick in there and literally

just rolled it out the hole, and boom.

No more invaders.

The ming went to these extraordinary lengths,

to combat a mortal enemy.

From space, satellites reveal vast grasslands to the north of the wall.

Wild enough today, in the days of the ming,

this was home to tribes of nomadic horseman.

The mongols.

These fearsome warriors had been attacking and pillaging

china for centuries.

The ming built the great wall to keep them out.

Now, 600 years later,

chinese experts are using science and technology to

reveal its secrets.

Sarah: Everywhere I look I see watchtowers on the top of the mountaintops.

Allan: Near a remote section of the wall.

Sarah: This view is unbelievable.

Allan: Canadian archaeologist sarah klassen is

on her way to meet one of the teams carrying out this

ground-breaking work.

Li zhe and professor zhang from tianjin university are

using drone data to create a 3d model of the entire

ming dynasty wall.

It's the most complete scan ever attempted.

Sarah: Without this technology doing something like this

would not be possible just look at the landscape,

you'd have to scale up all of those cliffs and map all of

these features it would take decades if it would even be

possible at all.

Allan: The new scans reveal the incredible achievements

of the ming in some of china's most extreme terrain.

Even on completely impassable ridges,

they still succeeded in erecting towers.

Sarah: Can you show me what you've done here?

Allan: And within the scans, new discoveries.

Li zhe has spotted mysterious openings,

along the base of the wall.

Using his data, I'm heading 120 miles east,

to investigate.

Allan: Look at this rugged landscape.

Check out this ridge, see the watchtowers up on the ridge,

that's where the wall is.

The wall is snaking all the way down to this saddle over here,

that's where I want to go...

Today, the wall here has crumbled away,

but originally it would've stood as tall as a three-story house.

Wow.

Can you imagine solid wall all the way down from this ridge,

then all of a sudden there's this door?

Clear through to daylight.

It's completely baffling, why would a defensive wall

have a doorway running right through it?

Yeah. This is a pretty small, compact space right now

but without all this rubble here this would have been the size of a person,

they would have just walked right through here.

The crazy thing is, you know, this is not some random

hole in the wall.

This thing is incredibly well built.

Look at all these bricks, just a perfect,

beautifully made arch.

So this was planned and the question is why?

Li zhe has found more than 50 of these doors

along this part of the wall.

And it's thought they could be used by scouts sent out

to spy on the enemy.

But the data are revealing something else.

The ragged edge revealed in this scan isn't a decayed doorway,

but the entrance to a hidden tunnel that was once bricked up,

before being smashed open.

Sarah: This looks really cool.

Allan: This new discovery is completely different from

any of the other openings li zhe has found.

Potentially a way of launching a sudden attack.

Allan: Smashing open this thin layer of bricks,

allowed the ming forces to ambush the enemy.

Before li zhe's discovery, experts had no idea these

hidden tunnels even existed.

It's an incredible find.

Allan: The latest technology is revealing that

the wall is far more than a simple barrier.

It's a complex military system.

The big question is, just how far does it stretch?

Using satellite images, we can reconstruct how the ming wall

extends far to the west.

From mountain ranges, through wild grasslands and into barren desert.

Right to its end, where the ming stopped building.

Here, at the very furthest reaches of their empire...

A huge construction.

Far greater than any of the thousands of towers along the way.

What is it? And what was it for?

To find out, I'm going to follow the wall to a far-flung

corner of western china.

allan: I'm investigating the secrets of

one of the world's greatest ancient icons.

Using satellite data, I've tracked the great wall all the

way from the mountains east of beijing to the gobi desert,

a 500,000 square mile expanse in the far north west of china.

Just over here I can see sections of the wall.

The feat of engineering required to build something so

far out here, in just this barren desolate environment,

just kind of boggles the mind.

After hours following the wall,

something massive emerges from the desert haze.

A mighty fortress.

Today, the modern city of jiayuguan is nearby,

but 600 years ago this fortress would have stood

alone in a desolate wilderness.

I never imagined I'd ever see something like this,

all the way out here in western china.

The great wall terminates in the mountains

just a few miles south of here.

Making this incredible structure the wall's final gateway.

The last fortress at the furthest edge of the ming dynasty's vast empire.

Look at how massive this is.

This rivals any gate or battlement anywhere in the

world at this time.

Here, you really get a sense of the ambition,

the engineering and the immense power of the ming.

A deep moat, walls up to 36 feet high,

and watchtowers on every corner form three layers of defense.

And even if the enemy does make it inside;

there are traps designed to create devastating kill zones.

You walk into this courtyard and if you're an

invading army, they can close those doors,

close those iron doors there and you're trapped here,

and all of a sudden they would just start raining down

fire and arrows from above,

and your invading force is doomed.

This is an ingenious military strategy all set and fixed in

the design of this incredible fortress.

It's massive, but also meticulously built.

The precision of construction here is amazing and,

you know, the emperor demanded that and there's this

legend that says the architect told the emperor,

he said I can tell you the exact number of bricks it will

take to build this fortress.

He said it would be 99,999.