All language subtitles for secrets.of.ancient.structures.s01e03.480p.web.x264.rmteam

(upbeat music)

- [Narrator] Throughout
the ancient world,

architectural
giants have embodied

the extraordinary ambition
of their builders.

- This is one of the most
intriguing structures

in human history.

- [Narrator] The vast
Colosseum reveals

sophisticated ancient Roman
engineering techniques

used to showcase unparalleled
displays of power and specs.

- There were amphitheaters
all around the Roman Empire,

but this one was the
greatest of them all.

- [Narrator] But
does the true key

to its success lie hidden
deep beneath the earth?

Clues hinting at
innovative materials

and building methods
used in the construction

of the Great Wall of China,

still linger in its
serpentine expanse.

- Stretching over
21,000 kilometers.

The Great Wall is
the longest manmade

structure in the world.

- [Narrator] What
unexpected ingredient

may have helped
cement its strength.

Within the imposing
structure of Malbork Castle,

Lies strategic design
and construction methods

that allowed it
to claim the title

of the largest brick
fortress in the world.

- The castle's
design incorporated

multiple layers of defense,

each one more challenging
to overcome than the last.

- [Narrator] But what
enigmas does it hold within

or perhaps beneath
its defensive walls?

(upbeat music)

(bright upbeat music)

In the eternal city of Rome,

the Colosseum stands as a
symbol of an ancient empire's,

relentless pursuit of grandeur.

It's weathered stone still
resonating with the echoes

of gladiatorial combat
and the roar of the crowd.

- I think the
Colosseum represents

sort of the greatness of Rome.

When you think about
the Roman Empire,

most people automatically
think of the Colosseum

and the fact that
it's still standing

after all this time, I
think makes it so appealing

and interesting and
inspiring to people.

(upbeat music)

- [Narrator] Though time,
nature and vandalism

have claimed nearly two thirds
of the ancient structure.

Its surviving walls
stand as a testament

to its former splendor.

- It sprawls across an
impressive six acres,

raiding as the largest
amphitheater ever built.

- [Narrator] Spanning an
impressive 189 meters in length,

and 156 meters in width.

The Colosseum's oval shape
consists of four stories

with its highest point
reaching a towering 48 meters,

boasting 80 entrances,
it's estimated

that it could hold between
50 and 80,000 spectators.

- The design of the
Colosseum is amazing

and it weaves together not
only structural engineering,

but mechanical water
engineering, theatrics,

everything that you can think

of to make this
production happen.

There's a lot going on here.

- [Narrator] In 80 CE, the
Flavian amphitheater destined

to become known as the Colosseum

stands ready for
its grand debut.

(upbeat music)

- People have always been
drawn to the Colosseum,

not just because it is an
architectural masterpiece,

but because of what
happens inside.

- The inaugural games
are a dazzling display

of Roman power and ingenuity.

- Chariot races, wild
beast spectacles,

gladiatorial combats,
all sorts of things

going on for a hundred
days, portraying the glory

of the Emperor
Titus and his family

and the empire as a whole.

- This was an
extraordinary spectacle

of slaughter and battle.

Thousands of animals
were involved.

Thousands of people in
these scenes of conflict

enslaved as well as criminals,

as well as professional fighter.

- [Narrator] Gladiatorial combat
the highlight of the games

pit skilled warriors
against each other

in tests of strength
and strategy.

- The Roman Empire was an
empire made through conquest,

so there was a lot of culture
around the strength of arms.

So it's not surprising that
for their own entertainment

it was focused on
the same thing.

- You could become a gladiator
if you were a free person,

but most of them were slaves.

But they could work their way up

if they were good gladiators,

and then they'd end up
gaining a lot of riches

so that they'd be able to
buy themselves out of slavery

and become real celebrities.
(upbeat music)

- [Narrator] These
battles though brutal,

a carefully choreographed
performances

that captivate the audience.

- For your average Roman.

Entering the Colosseum was
like an escape into grandeur

where they would witness
magnificent blood

thirsty entertainment.

- The number of
gladiators who died

is not as high as was
traditionally thought,

but still death was
a real possibility.

- [Narrator] But how
much of this spectacle

has been embellished
by the passage of time?

- Can't always trust
the historical sources

a hundred percent,
but it does seem

that these games were
particularly spectacular.

There were amphitheaters
putting on games

all around the Roman Empire,

but this one at the
center of the empire,

the embodiment of the empire
was the greatest of them all.

- [Narrator] But
where did the need

for these grand
violent spectacles

and a grand stadium to
hold them originate?

- The Colosseum when
it was built came

after a period of
tremendous instability.

This is the period of transition

from the earlier 500 years
of Republican government

moving into what becomes
increasingly an imperial state.

- The late Roman Republic
was a time of great turmoil

with the powerful fighting
amongst themselves.

It ended with Augustus
claiming basically the throne.

Augustus brings a
time of real stability

to the Roman Empire,
but it doesn't last long

because his relatives
who succeeded him

were not always all that stable.

Nero's rule was particularly
disastrous for Rome.

- Nero was a man who didn't
care about governance,

who was interested in
establishing his power,

but was ruthless in
his pursuit of it.

- Nero as an emperor
was very self-indulgent.

The entire empire was
there to serve him,

and he sets the tone for all

of the other major
families of Rome.

- [Narrator] The Flavian
dynasty and its first emperor,

Vespasian, comes
to power in 69 CE,

after a period of
civil war and unrest.

- When Nero was overthrown.

We have the year of
the four emperors,

Galba, Otho, Vitellius,
and Vespasian.

Vespasian was an older man.

He was an experienced general
and a successful general,

which garnered great
respect from the Roman elite

and especially from
the Roman armies.

He brought sanity
to the rule of Rome.

- After a period of
tremendous disorder

when people couldn't even
feed themselves very well.

When there was rapidly
increasing violence.

To have signs of stability

was incredibly important
and meaningful.

So here was an
opportunity for Vespasian

to establish himself as
the single most powerful

and unmatchable ruler of Rome,

the Roman Empire, but
also the Roman people.

- Part of the emperor's
control over the empire

had to do with
bread and circuses,

feed the people, and also
games to entertain them.

- A common person who's there
at the Gladiatorial games

might not have the best of
lives, but at the same time,

they're not risking
life for limb.

And so theory is that
you can produce morale

if you can show
somebody's worse off.

- Rome was a crowded place,

not a particularly
pleasant place.

Lots of potential for
uprisings, rebellions, riots.

- Keep the people happy,
give them enjoyment,

that lets them not think
about their daily lives.

And then we repeat this, right?

We go to our own sports arenas
and see top athletes compete,

root for our special teams,
root against the other teams,

or just go and enjoy
a really good game.

(upbeat music)

- You wanted a venue
like the Colosseum,

a big amphitheater
where thousands,

tens of thousands of people
could come to be entertained

by gladiatorial games
or battle reenactments,

or chariot races or
whatever it might be.

- [Narrator] Vespasian
identifies Nero's,

extravagant palace
complex, the Domus Aurea,

as the chosen site for his
massive engineering project.

- When the great fire
of Rome hit in 64 AD,

it wiped out a large
part of the city

and Nero's reputation took
a big hit as a result.

There are rumors that
he had sent his servants

to set the fire because
after the fire was over,

Nero thought it a good idea
to build a golden house

on the burned out
remains of Rome.

- Nero's massive palace
complex symbolized

his extravagance in the
eyes of Roman people.

They saw this as a monument
to imperial self-indulgence.

- It was a heartless
exploitation

of what had devastated
the people as a whole.

(upbeat music)

- [Narrator] The
space's decision to
construct the Colosseum

on the site of Nero's
palace is a calculated move.

- Vespasian was starting a
new dynasty and he had to show

himself superior to
the previous dynasty.

If he could exploit what was
disreputable in Nero's rule

and do something for the
people, something glorious,

spectacular, then that
would give his dynasty

the position he wanted for it.

- So here we have
this palace co-opted

to build a public space, a
public place of gathering,

that belongs to
the Roman people.

- Everybody's invited,
everybody can come.

The emperor's there,
the leaders are there.

They're in their own boxes.

Just like we have box seats now,

where people with more means
don't sit with the rest of us.

So in some ways it is
reinforcing the social strata

within the Roman Empire,
but for the common person

who's in there
watching the games,

they see themselves as doing
something that even the emperor

is doing and there's
not much in their lives

that they get to do,
especially entertainment.

That is entertainment
for the emperor.

(upbeat music)

- [Narrator] Carrying
out Ian's ambitious plan

would require a solid foundation
to bear the immense weight

of the proposed structure.

- It's really important that
we have really firm foundations

so our buildings
don't settle and move.

A great example of a building
that had a terrible foundation

is the leaning tower pizza.

We had this building where the
foundations weren't adequate.

The soils have flowed
under the building

and now the building
leans significantly.

- [Narrator] But for
this new amphitheater,

there are significant
challenges to be met.

The Vespasian chosen
site at the center

of Nero sprawling Domus
Aurea is a marshy area

containing a 20,000 square
meter artificial lake.

- So you picked a site that
is on a lake basically,

so you have to get
rid of that lake first

before you can even
build the structure.

That means dewatering that
lake, looking at that soil,

that might not be
great for building on,

and increasing its ability to
bear a giant structure on it.

It's a big project.

- [Narrator] Once they've
drained the artificial lake,

they excavate the site 12 meters
deep down to solid ground.

- When we are talking
about building a structure

like the Colosseum
on a drained lake,

we have a lot of
issues with the soils,

a lot of clay, a lot of sand.

We're gonna have to dig down
through those silty clay layers

to something more stable.

We're moving 220,000
metric tons of material.

This is something we
can easily do nowadays,

but in that period it
really is mind boggling

to think about it being
done by manual labor.

- [Narrator] They then
construct a foundation

over 12 meters thick consisting

of multiple layers of concrete.

- Concrete is an
amazing material.

You have this material
that when wet is flowable,

so you create a mold to
pour that concrete into,

and then it sets up reasonably
quickly into something

really strong and
really durable.

- This is really
a great example.

One of the first real engineered

is when we're really starting
to produce real concretes

and really have some
understanding of how they work.

- [Narrator] The Colosseum's
concrete foundation is credited

as a key factor in its
remarkable longevity,

providing a solid
base for the tons

of other materials
placed on top of it,

including approximately
99,000 cubic meters

of travertine stone,
300 tons of iron clamps,

and a million bricks.

The piece is still
standing today,

offer critical insights into
its construction techniques.

- We can see evidence of the
backbone of the structure,

these massive blocks that served

as robust load-bearing pillars.

These blocks are punctured
by numerous holes,

remnants of iron
clamps and dolls

that once held the
stones together.

Over the centuries, these
metal fixtures were removed

and repurposed, but they still
leave behind their marks.

- [Narrator] The walls
and stairs are crafted

from a combination
of bricks and tough,

a softer volcanic rock providing

both strength and flexibility.

- The Colosseum has a really
interesting cross section.

It's structurally
really capable.

You can easily identify the
series of arches and vaults,

and they use the materials
in a configuration

that makes good sense to
carry the weight of the people

who would be visiting
the Colosseum

and the materials themselves.

- [Narrator] What
techniques and tools

did the ancient Romans have to
erect these impressive walls,

arches and vaults on a structure

that reached a height of 48
meters at its highest point,

- Many ancient
civilizations started

to develop technology
around mechanics.

They understood incline planes,

so ramps and why they
help move large objects.

But when you're moving
a very large block

up an immense distance, you
have to have a huge ramp

for it to be an
effective incline plane.

And that means that it's really
hard to build vertically.

To build vertically, we
need a different technology,

and that's where cranes come in.

Cranes allow us to
lift objects vertically

instead of pushing
them up incline planes,

- [Narrator] But uncovering
conclusive evidence

about the ancient Romans
building tools is challenging.

- Because Roman cranes
were made from wood,

a perishable material.

Complete remains are
virtually non-existent.

Only small components like
pulleys, cable pieces,

and iron reinforcements
have been found

in the archeological
exploration.

- We have really good
historical records

from the Roman period,
and so even though

we don't necessarily have
all the physical tools

and we still have an idea
of how things are done,

either through
writings or drawings,

that allows us to
try to piece together

how some of these
structures came together.

- [Narrator] The
earliest crane technology

can be traced back
to the ancient Greeks

in the sixth century, BCE,

whose machines revolutionized
construction techniques.

- The technology of cranes
really comes down to pulleys.

And pullies are really neat.

So if I take one single pulley
and I put a load on one side,

if I have a hundred pounds here,

I'll have to pull with a
hundred pounds here to lift up.

But what I can do is I can
put a pulley at the top

and a pulley at the bottom.

What happens is each
of the ropes that loop

around the pulley start
to carry some of the load.

All of a sudden, I
need much less force

pulling down to lift
a very huge object.

So no longer do we have
to have the 100 pounds

lifting 100 pounds, I can
have 400 pounds of people,

pulling on a rope
lifting a six ton block.

(bright upbeat music)

- [Narrator] But even the most
advanced lifting techniques

used by the ancient
Romans would require

significant human power.

- Slave labor was a reality
throughout the ancient world,

and certainly the Colosseum
is a perfect example of that,

and it was drawn from
all parts of the empire.

But in particular, we think
from the enslaved populations

that were taken out of Jerusalem

following its conquest in 70 CE,

and we think it's upwards of
60,000, to a 100,000 people

from Jerusalem were brought.

- [Narrator] Upon
its completion,

under Vespasian's son Titus,

the Colosseum would be defined
by its gladiatorial contests

and animal hunts all
taking place on a floor

made up of a wooden
platform covered in sand.

But those early years would
feature another spectacle,

one that would
transform that floor

turning the Colosseum into
something entirely unexpected,

a stage for grand naval battles.

- One of the most
impressive spectacles

that the Romans loved
were the Naumachiae.

Often they would reenact
a famous historical

naval battle and the
people loved them.

- [Narrator] These elaborate
theatrical productions

typically involved large
artificial basins or lakes

where ships manned
by prisoners of war

or condemned criminals would
engage in dramatic sea battles.

- And these naval battles
actually became one of the new

innovations of spectacle during
the time of Julius Caesar

to celebrate his own victories.

Over time, however, these
were getting more dramatic.

They were getting
more elaborate.

They had to keep
innovating in order

to keep the attention
of the populace.

- There are historical
references to naval battles

taking place in the Colosseum,

but we're not absolutely
sure they really did.

- [Narrator] Despite ancient
writings by Cassius Dio

and poet Martial to back it up,

some historians
remain skeptical.

- There's a lot written
about it historically,

which leads you to believe

there's gotta be
some truth about it.

But in terms of actually
nailing down the science

of how it was done, there's
still some debate around that.

- [Narrator] These
spectacles are so grandiose

that they almost
seem impossible.

- If you were just a standard
person who was there,

the idea that it could be
flooded to have naval battles,

that's something that
couldn't easily be expected.

It almost feels like magic.

- [Narrator] How could
the ancient Romans

have achieved such watery
spectacle within the Colosseum,

with the technology available
to them at the time?

- It totally changes
the landscape

of how you're gonna design this,

and you have to start weaving
in the mechanical systems

to deliver that water,
manage that water,

take that water away.

- One of the things about water

is it's very difficult to pump

and it takes an immense amount
of energy to pump water.

So we need a
different technology

and that's where
aqueducts come in.

So what an aqueduct is,
it's a bridge system

that brings water from higher
elevations into another area

that could use the
natural gravity

and the flow of
water to get water

to go where they wanted it to.

- The Roman Empire is
filled with aqueduct.

It's one of the things you
see that still exists today.

The Claudian aqueduct
alone could discharge

up to 2200 liters per second.

One of the theories is that
they were able to basically

divert some of the
water from the aqueducts

to the Colosseum, which
would've filled it very rapidly.

- [Narrator] Another theory
posits that the Colosseum

had a sophisticated system

of underground chambers
and sluice gates.

- Basically, a sluice gate
is kind of like a big valve.

It basically is a door that
prevents water from flowing,

and when we open that door,
the water can flow in quickly.

So sluice gates are
really a great way

in combination with reservoirs

to fill the Colosseum
with water very quickly.

- The Colosseum's
original underground area

is altered beyond recognition,
making it almost impossible

to reconstruct exactly how
flooding would've worked,

but could the answers be
found within this massive

renovation itself.

- [Narrator] Beneath the
floor of the Colosseum today

lies a complex labyrinth
of underground tunnels.

After decades of neglect,

it has finally been
unearthed by archeologists.

- How did the Romans
build such a complex

underground structure?

And what was it for?

- [Narrator] In 83 CE, Titus's
successor, Emperor Domitian,

commissions builder heter to
build an intricate network

of tunnels and lifts
beneath the amphitheater,

called a hypogeum.

- The word hypogeum taken from
Greek means under the earth,

so the term could
have included anything

that was built under the
floor of the Colosseum.

- [Narrator] Through
painstaking analysis,

archeologists are
gradually uncovering

how herter is ingenious
engineering revolutionized

the spectacles at the Colosseum.

- The building of the
hypogeum a few years

after the opening
ceremonies marks a move away

from naval battles
to a focus much more

on gladiatorial combat and
on human and animal combat.

They built in lifts and
elevators that will allow

for surprise moments
in the spectacles,

in the form of animals
and gladiators,

being able to move up
quickly onto the floor

of the Colosseum to
join in a combat.

- There's this whole
city of activity

that happens under the stage,

and the whole system
worked together

between a series of
pulley and lifts and ramps

and all sorts of different
elements that allowed

sort of this surprise
entertainment to occur.

- It's really quite impressive
when you have, you know,

six people standing
on a platform

all of a sudden come
up out of the ground.

And it would be astonishing
to people of the time.

- In 404 CE, the gladiator
games were discontinued

and the Colosseum
fell into disrepair.

- The Roman Empire falls
over time and the Colosseum,

along with the empire, will
find its purpose diminished.

It will be neglected
in the overrun.

It will eventually be converted
into a Christian space

by the Catholic church
as a way of showing

the conquest of the
Christian tradition.

And over time we'll see it
repurposed again and again.

But to this day,
it still stands,

and I think we have to keep
in mind those long histories

to really understand its legacy.

- [Narrator] Despite
the passage of time,

the Colosseum continues
to evoke the spirit

of the Roman Empire
in both grandeur

and the darker aspect
of its history.

And while it's
difficult to contend

with the engineering might
of the ancient Romans,

another ancient structure
rivals even the Colosseum

in its sheer scale and ambition,
the Great Wall of China,

winds majestically across
mountains, deserts, and planes,

symbolizing the strength
and visionary ambition

of a civilization determined
to safeguard its heritage.

- Stretching over
21,000 kilometers, the
Great wall of China

is the longest manmade
structure in the world.

- It remains a powerful symbol
of China's imperial past,

but it's also a powerful
symbol of the history of China

as part of a diverse,
multi-faith, multi-ethnic world

in which they had to engage.

- [Narrator] Contending
with a wide range

of challenging terrains, the
wall's architectural styles

and construction
techniques are tailored

to the various
landscapes it traverses.

- You're confronted with
so many different things

that you can't anticipate,
but you have to react

to what you encounter
and work with

what you've got in a remote
area building this massive wall.

- The construction
methods of the wall

evolved massively over time.

So earlier sections
reveal rammed earth, wood,

and stone used in construction.

Later sections of the wall
reveal much more sophisticated

construction methods with
bricks and cuts stone blocks.

- Archeologically speaking,

there's a lot of
history and information

that is sort of entombed
within the construction

of this wall, and it
can tell us a lot about

the history of China over
the period of construction.

- [Narrator] But even
after centuries of study,

the Great Wall continues to
evade full comprehension.

- There are some parts that
are extremely well preserved

and there's been
some reconstruction,

but there are also
parts of the wall

that are just crumbling
and dilapidated.

So you've got different
segments that look different

depending on sort of what state

of disrepair they might be in.

- The estimate as much as
30% of it has disappeared,

which means we're
really having to rely

on the remaining 70%
to unlock its history.

And that poses challenges

because we don't have written
documents in many cases,

this is an enormous wall,

but all the sections
are different,

and clearly they were designed
to serve different purposes.

So what were they
intended to do?

(bright upbeat music)

- [Narrator] Propped up
along the mountain ridge,

one of the most remote stretches
of the Great Wall of China

offers a unique window into
the secrets of its past.

- This is one of the most
remote and challenging sections

of the Great Wall, just
given the natural landscape,

and so it's essentially been
untouched for centuries.

- [Narrator] Recent restoration
efforts have ignited

new interest in this
previously neglected section.

Stone tablets unearthed
on the Jiankou section

bear Inscriptions that once
decoded offer critical insights.

- Inscriptions show that several
beacon towers and the walls

connecting them were
constructed on vastly

different timelines.

This means this section
took more than four decades

to build, suggesting
a phased approach,

adapting to changing
needs and challenges.

- Anytime you uncover
a historical record,

like actual written text or
some sort of written format

is really exciting because
then you can start to validate

what you're seeing and
what you're finding

with that historical record
or what's been written.

- [Narrator] The concept
of border walls in China

dates back to the
seventh century BCE,

during the tumultuous
Warring states period.

- We have many different
power structures,

some of which are
competing with one another,

some of which are
cooperating with one another,

but they're also
having to engage

with other cultures nearby.

(upbeat music)

- [Narrator] During this
time, the individual states

all construct their own walls.

After unifying China in 221
BCE, Emperor Qin Shi Huang

orchestrates a massive
project to connect and expand

the existing walls into a
more cohesive structure.

- This marked the
birth of the Great Wall

as a unified concept.

- [Narrator] In the
centuries that follow,

successive dynasties
continue to strengthen

and expand the wall,
gradually transforming it

into a more sophisticated
defense system.

But it was the Ming Dynasty
founded in the 14th century,

that would establish
the monumental edifice

we recognize today.

- The Ming Dynasty, of
course, is very well known

to many of us through
its cultural legacy

in the form of a beautiful
ceramics and so forth.

But it was at the time
also a new dynasty

that was trying to
distinguish itself

from previous dynasties
by celebrating its role

as an administrating power.

It was very important to
them to establish the rule

in the eyes of the people
they were governing as stable,

as concerned about peace.
(upbeat music)

- [Narrator] The Ming
Emperors take wall building

to new heights quite literally,

but who are they so
determined to keep out?

With an average height
of eight meters tall,

the Great Wall is often hailed
as an impenetrable barrier,

a monument to
ancient engineering

that kept invaders
at bay for centuries.

- But was the wall
really impenetrable?

- [Narrator]
According to legend,

the Great Wall was
breached multiple times

throughout history,
including 14 times,

by the Mongolian army in
the early 16th century.

- We think of
walls historically,

we tend to think of
them as defensive

or protective measures only,

but walls are not simply
to keep people out,

they're to regulate your
relations with others,

some who are hostile,

but some who are
simply their neighbors,

who they have to also
have communication with,

trade with, and so forth.

So it's also actually a border,

a boundary that
is like a gateway.

- One of the things with
large structures like walls

is it's not only a
barrier to our enemies,

but a barrier to ourselves.

So you always want to have
some type of pass through

through your structure so
that you can get out of it.

- [Narrator] Besides the
hundreds of official passes

through the wall, recent
discoveries unveil ruins

of over 130 hidden doors
within the Great Wall,

further challenging the notion
of its absolute security.

- Basically built arch
tunnels through the structure,

so that would be self-supporting

and they'd be able
to make an egress out

the other side of the wall.
(bright upbeat music)

- [Narrator] Some of the
most intriguing passages

have exits designed with
a careful camouflage.

- The exits facing the enemy
are constructed with brick

making them near impossible
to detect from the outside.

However, from the inside,
they're hollowed out,

allowing the defenders
to launch surprise

sudden attacks on the enemy.

- [Narrator] These discoveries
revealed that the Great Wall

was not a completely
closed off structure,

but one that could be covertly
and strategically opened.

- Although previous dynasties
had expansionist policies,

the Ming Dynasty
adopted a defensive one.

- [Narrator] They concentrated
on fortifying their borders

and consolidating control
over their existing territory.

This defensive focus,

particularly against
the northern threats,

led to significant
investments in the Great Wall,

transforming it into a
complex multi-layered

defense installation.

- It was a big building dynasty,

and so the wall in this
time became very important

as a way of broadcasting
its interest

and being a protector and a
defender of the population,

not as an expansionist power.

- [Narrator] At its peak,
the Great Wall boasted

approximately 25,000
towers along its length.

Typically standing 10 meters
tall, we find these towers

primarily on elevated
points, hilltops, ridges,

and mountain peaks, allowing
for a 360 degree view

on the surrounding terrain.
(upbeat music)

These towers serve
multiple purposes

as defensive structures
and observation posts,

but they also function
as signal stations.

- These towers were
strategically placed,

enabling rapid communication
across the length of the wall.

(upbeat music)

- [Narrator] Using
smoke signals by day

and fire beacons by
night, guards can
quickly relay messages

from station to station.

- Signal towers were very
important to maintaining

local power from
a great distance.

Every five kilometers, there
was another signal tower.

Travel on foot would
take a long time,

but to communicate by
smoke signals means

that they could quickly learn

if there was some serious issue
on the border and mobilize.

- [Narrator] These towers
typically have three stories.

While the top floor is used
for observation and signaling,

the first two floors serve as
living quarters for soldiers.

- The soldiers who
were sent to the wall

came from all sorts of
other parts of China.

They're stationed
on parts of the wall

for long periods of time.

So what is that life like?

(upbeat music)

- [Narrator] At the top
of one Beacon Tower,

archeologists found a hearth,

likely built to help
soldiers endure harsh winters

and to use for cooking.
(upbeat music)

This discovery offers a
window into the daily lives

of the soldiers who called
these watchtowers home.

(upbeat music)

- The lives of these soldiers

were defined by
vigilance and endurance.

They were isolated,
removed from family,

so they were lonely.

They were also on high alert,

constantly aware of
a potential attack.

- So you're supposed to be in
a constant state of vigilance,

but what you end up
getting is an awful

lot of operational fatigue.

It's the same thing
day in and day out.

You're expected to be
ready for the one time

something might happen
in what a couple years.

- [Narrator] The construction
of these towers on elevated,

often remote locations
presented unique challenges

to ancient engineers
and builders.

- Across the length
of the Great Wall

there's 25,000 of
these signal towers,

and they're built at
strategic locations,

really difficult terrain.

We're talking on
mountain ridges on hills,

and just thinking about
building something

in this remote location
with not a lot of materials,

not a lot of access,
that's a huge undertaking.

- [Narrator] Throughout
its vast history.

The Wall's construction is
estimated to have required

an astonishing 100 million
tons of stone, bricks and mud.

But the secret to the
longevity of the Great Wall

may be in the stuff that
holds it all together.

- The use of mortar in
the Great Wall of China

is really what helped
preserve it for millennia.

So mortar not only acts
as part of the strength

of the structure, but it acts
as a seal to keep the elements

out of the actual
structure itself.

So if I don't have mortar,
what happens is water

gets in and it freezes
and it expands,

and it very quickly breaks
down large structures.

(upbeat music)

- [Narrator] Centuries
before modern science

unraveled its unique properties.

Ancient Chinese builders
harness the power

of a remarkable albeit
unassuming material.

(upbeat music)

- The Chinese were
using a special mortar

that they had invented.

It was using sticky rice
as a main constituent

to really make this
mortar quite tough.

- Sticky rice has sugars in it.

Sugars are a lot
like modern polymers,

and we can get what we
call polysaccharides,

which are even
longer sugar trains

much more similar
to polymers again,

which is what's in sticky rice.

So you take a mortar material,

which isn't particularly
good, it's strong enough,

but it doesn't weather well.

And then you take something
like the polysaccharides

in sticky rice, which aren't
gonna be strong enough

to support the wall,
but seal really well.

And all of a sudden when
you mix these two materials,

you have an engineered material

that is now able to provide
all the necessary conditions

to act as an excellent mortar.

- [Narrator] Scientists in
China studying this mortar

found it to be the
world's first example

of composite mortar,

combining both organic
and inorganic materials.

- This mortar is quite a
dense mortar that prohibited

this sort of cracking
or failure of it,

which allowed it to
stay intact and prevent

vegetation growth
from happening.

- It's a really
interesting and distinct

cultural dimension of the wall.

It shows an adaptation
to local resources

that it sets it apart from
any other monumental building

that you'd see for
example, in Western Europe.

- [Narrator] The sheer scale
of the Great Walls construction

is almost unimaginable.

Chinese engineers and
builders coordinated

this gargantuan
task using methods

that were greatly
dependent on the terrain

and available resources.

- On flatter land, they
would've used horses

and oxen and in drier
climates, even camels.

But ultimately, this great wall
was built with human hands.

- We didn't have, you
know, the excavators,

the earth moving equipment,
the trucks, the cranes,

that are in modern societies.

So everything is
done by human power.

The Great Wall of China is
a project that literally

lasted centuries, and this
takes millions and millions

and millions of man
hours to construct.

- Many of them
would've been enslaved

or prisoners or paid helpers.

But the bottom line is
that this kind of project

at the end of the day
relied on human labor

that would've involved the
transportation of materials

in many cases from very,
very long distances.

- [Narrator] While
the Great Walls stands

as a testament to
human ingenuity,

it also bears a darker
legacy, one that has earned it

the grim title of the
world's longest graveyard.

- The human cost of building

the Great Wall of
China was staggering.

As many as 400,000
people may have died

during its construction.

Many of these
workers were convicts

or peasants forced into labor.

They faced brutal conditions,
insufficient food,

treacherous terrain,
and harsh weather.

- [Narrator] The huge numbers
of deaths led to the rumors

of the bones of dead
workers being used

in the construction of the wall.

- While there would
be many deaths

during the construction
of the Great Wall,

we don't actually find
evidence that supports,

you know, bodies were
thrown into the wall

during construction or buried
or entombed in the wall

as it was being built.

And I think it's just part
of oral history or rumors

being spread that gets
translated over time.

- In a lot of sites like this,

there's a lot of
wonder surrounding it,

and this mythology turns into
folk stories and legends.

So from an archeological
perspective

is trying to decipher
fact from fiction,

and we can do that through
the archeological record.

(upbeat music)

- [Narrator] As researchers
continue their attempts

at unraveling the
Wall's mysteries,

it becomes clear that the Great
Wall of China stands today

as far more than the remnants
of a military barrier.

And while the Great
Wall serves as a symbol

of defensive ingenuity
spanning millennia,

another formidable
structure in medieval Europe

tells a different story of power

and protection against
its adversaries.

(upbeat music)

In Northern Poland, looms
one of the most formidable

medieval fortresses
in the world.

(upbeat music)

- This is the large brick
castle by land area.

Some 52 acres containing an
estimated 30 million bricks.

- It's surrounded by
moats and defensive walls.

It is a site to behold.

- [Narrator] Once the seat
of power for the order.

This Grand Castle was designed
as an impenetrable bulwark

against external threats.

- Why was building on
such a massive scale

so important to important
to the Teutonic Knights?

- Was it a practical measure

because of their
growing numbers,

or did it represent
something to do

with their grand ambitions?

(upbeat music)

- The Teutonic Knights
were a formidable Catholic

organization that emerged
in the late 12th century

during the Crusades.

- The Teutonic Knights
represent a new type

of religious order, half
monk and half knights.

Knights that take monastic vows.

- The Teutonic Knights were
one of the many military orders

which are formed amongst
the European nobility

to go and rescue Jerusalem

from the Muslim
rulers of the time.

- In the 13th century,
the order begins to expand

and take on a new purpose

with the so-called
Northern Crusades.

At that point in time, the
Baltic region of Europe

was still largely pagan,
and the Teutonic Knights

took it upon themselves
to change that.

It became the basis
for them to set up

the first monastic
state for the order.

- They essentially introduced
a theocracy in Prussia.

A theocracy is a
government in which church

and state are collapsed.

So the Teutonic Knights
themselves were the rulers

as a religious
order of the state,

which they carved
out for themselves.

And this is a society
that they formed

and that was centered
at Malbork Castle

- [Narrator] Construction
of Malbork Castle

is initiated by the
order around 1274,

following their success
during the Prussian Crusade.

- Building a castle on such
a large scale was symbolic.

It was letting the world know

that this was a
serious organization,

this was an important
organization,

and they were making
their mark on the globe.

- Castles are often built
over a long period of time.

They'll have one structure

and then they'll keep
adapting them and innovating

and adding to them
as their needs change

and as they face new
challenges over time.

So Malbork Castle is a
good example of that.

- The High Castle,
the oldest park,

served as the monastic
center of the complex,

embodying the orders of
religious foundations.

- [Narrator] Malbork
Castle was more

than just a military stronghold.

It was a city unto itself,

housing hundreds of knights,
servants, and craftsmen.

- In 1309, the Teutonic order
moves their headquarters

into Malbork Castle.

- [Narrator] The arrival
of the order's Grand Master

necessitates the construction
of an entirely new section

of the fortress.

- The Middle Castle
was added in 1309,

and was built to accommodate

the increasing
number of knights.

And the grandmas court
featuring grant halls

for ceremonies and receptions.

- As their power
territorial control expands,

their numbers begin to swell.

At their height it's
estimated that Malbork Castle

was home to 3000 knights.

- When we look at the
various military orders,

often they were traveling
to other countries,

and one of the things
that kept a military order

together was the idea
of having a home.

So in building this home base
for the Teutonic Knights,

it actually helps knit that
brotherhood stronger together.

- The low castle, also
known as the Outer Castle,

was the final edition.

It was constructed
during the late 14th

and early 15th centuries
and served economic

and defensive purposes.

- The growing complexity
of Malbork Castle

represented the
growing complexity of
the Teutonic Order.

No longer were they
just knights, now
they were diplomats,

now they were administrators,

now they were religious leaders.

- [Narrator] But the grand
scale and strong defenses

of Malbork are necessitated
by the formidable enemies

of the Teutonic Knights.

- Malbork Castle is a physical
symbol of their strength.

It looks strong and imposing.

It looks like it's
going to last forever.

And these are all the
features that the knights

wanted their enemies
to be afraid of.

We are strong, we
are impenetrable.

We will always last.
You should fear us.

- [Narrator] In 1410, the
Teutonic Order finds itself

at a critical juncture
as the Battle of Grunwald

marks a dramatic turning
point in medieval history.

- This was a monumental clash

between the Polish
Lithuanian Alliance,

and the Teutonic Knights.

- [Narrator] The alliance
was formed by the kingdom

of Poland and the Grand
Duchy of Lithuania in 1409.

After a series of
territorial disputes

with the Teutonic Order led
to a declaration of war,

- The alliance doesn't just
wanna win on the battlefield,

they wanna dismantle the
entire Teutonic Order.

To do that, they have
to take the castle.

Some 39,000 soldiers at the
Polish Lithuanian Alliance

gather outside the castle.

Just 27,000 knights remain
inside the defendant.

- [Narrator] The
alliance goes on to claim

a decisive victory
in the battle itself.

With most of the Teutonic
leadership killed

or taken prisoner, despite
the defeat on the battlefield,

the Teutonic Knights are
able to keep Malbork Castle.

But what secret lay
within this fortress,

allowing the order to defend

against such a formidable force.

- The castle's design
incorporated multiple layers

of defense, and each
one would've been harder

to overcome than the last.

- If you have a simple castle
with a single exterior wall,

once that wall is
breached, you're done.

So castles need multiple
technologies to prevent invaders

from capturing
them very quickly.

So once the first
wall gets breached,

you can move back
behind another wall,

and then when that
gets breached,

you can move again
behind another wall.

- [Narrator] These
were further reinforced

by both wet and dry moats,

adding extra depth to
the castle's defenses.

- Basically, your attackers
actually have to build

some kind of bridge
structure to attack the wall,

and all the time
they're constructing

or moving that
structure into place,

you're free to attack
from the castle walls.

- [Narrator] Towers serve
jewel purposes as watch towers

and strongholds, allowing
defenders to spot

approaching enemies from afar
and providing strong points

of resistance during an attack.

The fortified gates are
particularly impressive,

featuring a combination
of drawbridges,

portcullises, and
ironclad doors.

This multi-layered approach to
gate defense makes breaching

the castle's entrance an
extremely daunting task.

While the visible
fortifications are impressive,

medieval castles
often held secrets

beneath their
imposing exteriors.

Legends persist of a network

of hidden tunnels
beneath the castle.

- These underground
tunnels were fairly common

in these types of structures.

Not only would these tunnels
be used to get people

in and out, but they
could be used for things

like supplies, food,
weapons, ammunition.

(upbeat music)

- A story has emerged
of a terrified pilgrim

who seeks to escape
during the siege.

And on his exit, he comes
across a line of ghostly knights

who are allegedly headless.

- He's already gonna be fearful

because of the whole
warfare and siege

that's going on and
needing to make an escape,

you're in fight or flight mode.

So if he is afraid
and he hears things,

he's gonna start imagining what
could have made that sound.

- The terrified pilgrim
flees, and allegedly,

the knights close off the
tunnel keeping it hidden

and underground ever since.

- Ghost stories are very
common in a lot of castles

because of their secret
tunnels and underground spaces.

These were places
of cultic worship.

These were places
where you would hide

away from persecution.

These were also places
where spirits were believed

to live in many
different cultures.

- [Narrator] After over
a century of power,

the Teutonic order
never fully recovers

from the consequences
of their defeat

at the Battle of
Grunwald in 1410.

- The Teutonic Knights
managed to successfully

defend Malbork Castle,

but the aura of their
invincibility was badly shaken.

- [Narrator] The order would
face a further setback in 1457,

during the 13 years war, fought
once again against Poland.

In a dramatic twist,
Teutonic mercenaries unpaid

and seeking compensation,

seize the castle and sell
it to the Polish King.

This marks the end of
Teutonic control over Malbork,

transforming it into a
Polish royal residence

and a symbol of shifting
power in the region.

The castle will go on to
withstand further conflict

and later become part
of Prussian territory.

Following the partition
of Poland in 1772,

despite extensive damage
during World War II,

Malbork Castle is
meticulously restored

and now stands as a UNESCO
World Heritage Site.

- Today, the castle serves
as a bridge retreat,

past and present, offering
insights into the ambitions,

ingenuity, and perhaps
fears of those who built

and defended it centuries ago.

(upbeat music)

- [Narrator] From the
grandeur of Rome's Colosseum,

a testament to the
might of ancient Rome

and its ability to
entertain thousands,

to the great Wall of
China destined to protect

an empire for millennia to
Malbork Castle's, embodiment

of the grand ambitions
of the Teutonic Knights.

These monumental works stand
today as inspiring symbols

of the sheer scale
of human ambition.

(upbeat music)