All language subtitles for Ancient.Engineering.S02E08.1080p.AMZN.WEB-DL.DDP2.0.H264-chr00t_track3_[eng]

- [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 it's reality.

- [Narrator] Many of today's
incredible achievements

rely on breakthrough
technologies,

first devised by
ancient engineers.

- It's astounding how
they achieve 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.

- 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 they're genius

laid the foundations for
everything we build today.

[exciting music]

Today, across the planet,

countless engineering marvels
for antiquity still stand.

- We wonder the great
engineering marvels,

the great engineering
technologies that
are all around us.

- [Narrator] The
Great Wall of China,

traversing over 13,000 miles
through arduous terrain.

Machu Picchu, built
impossibly high

atop of Peruvian mountain.

The Coliseum.

Capable of holding over
50,000 roaring spectators.

- History is about cultures,
about people who create things,

who are then overthrown
and forgotten,

but then rediscovered.

- [Narrator] These achievements

have rightfully claimed
their place in history.

Yet for every pyramid,
Pantheon, or Parthenon,

there are lesser
known achievements

that also deserve recognition.

- Every year, we uncover
new ancient engineering

that adds to that
narrative that we have

about what engineers of
the past could achieve.

- [Narrator] The invisible
effects of technology,

which either lie underground,

are hidden beneath the
surface of the architecture,

or are only perceptible with
senses other than sight.

- We may find it
in monumental form,

we may find traces of it,

but it is part of the
story of humankind.

- [Narrator] Hidden innovations

that also employed
precision engineering,

to underpin incredible
achievements.

- So much of what ancient
engineers have achieved

has flown under the radar.

These are history's
hidden marvels.

- [Narrator] For
2 million years,

our earliest ancestors lived
life constantly on the move.

- Primitive societies
would've relied for sustenance

on gathering and hunting.

So a mixture of berries,
fruits, nuts, seeds,

as well as hunting wild animals.

So when they've exhausted
supplies in one area,

they'd be moving
onto another area.

- [Narrator] But then
around 12,000 years ago,

came a development that
would change everything.

Agriculture.

First emerging in
the Middle East

in an area known as the
Fertile Crescent, by 6,500 BC,

the so-called
neolithic revolution

saw agriculture
arrive in Europe.

And for the next two millennia,

it swept across the
continent from east to west.

- Across the inhabited world,

people started settling down
planting crops and staying put,

and that led to people building
houses, villages, towns,

cities, civilizations.

- [Narrator] The new sedentary,
agricultural lifestyle

brought a steadier, more
predictable supply of food.

But it also introduced
new challenges

for those early farmers.

- Hunter gatherers take
water from the stream or pool

where they happen to
be, and then move on.

But if you are a farmer,
then you're tied to the land,

and you had to find
a way of ensuring

that water supply
was always available.

- [Narrator] Many early
settlements were established

near streams, rivers, or lakes.

But in more arid environments,
or during periods of drought,

some neolithic
communities tapped

into a different source
of water altogether.

- Hidden below the ground
is what's in as groundwater.

Rainfall is trapped
typically in a layer of clay.

So it's possible
to dig a well down

to that particular level.

And it will naturally
fill with water

that can be drawn
on a reliable basis.

- [Narrator] Wells were
bored into the ground

at depths of up to 45 feet.

But these deep holes
filled with water,

were structurally weak
and prone to collapse.

- In order for these
wells to survive,

it was necessary to
line them in such a way

to hold back the
earth from collapsing.

And various materials had
been used throughout history,

stone, and brick,

but these neolithic
farmers used timber.

- [Narrator] The remains
of over 100 neolithic wells

have been found across Europe.

In 2018, during the
construction of a motorway

in the Czech Republic,

one extraordinary discovery
transformed the modern view

of just how far back in time
these structures were built.

[thrilling music]

It has become known
as the Ostrov Well.

- What's remarkable
about this well lining,

is that it was dated
using dendrochronology,

which is where we look at
the sequence of tree rings

to give us an absolute
date of construction.

And in this example
is 7,278 years old.

And that makes it the oldest
wooden structure in the world

to be dated using this method.

- [Narrator] Existing at a
depth of five and a half feet,

this ancient timber
lining helped to ensure

that the collected
groundwater did not silt up.

- It's really
tremendously early,

thousands and thousands
of years before the Greeks

or the Romans or
other civilizations.

- [Narrator] Made from oak,

it's not just the well
lining's great age

that is impressive.

The sophistication of
the carpentry skills

needed to construct it
are also exceptional.

To form the box-shaped lining,

longitudinal mortices were
cut at 90 degree angles

into four vertical
oak corner posts.

Seven planks, each
with end tenons,

were then inserted horizontally

to create a structure measuring

about four and a half feet high,

and two and a half feet wide

that stabilize the
walls of the well.

- But these neolithic
farmers only have had

polished stone axes to
build these wells with.

- And the level of
preservation is so good

that we can see the
problems that they had

splitting the timber
and dressing it down

without metal tools.

- So what is incredible
is how they're able

to achieve really very
sophisticated jointing.

It is an absolute
marvel of carpentry.

- [Narrator] The hidden
genius of well linings,

like the one at Ostrov,
allowed neolithic settlements

to thrive right across Europe.

And set in place a
method of construction

that would be adopted
by civilizations

throughout the continent.

- And these well linings
that they may seem simpler,

are a really good
technological solution

to provide a stable water
supply to a growing community.

They wouldn't have
survived without it.

- [Narrator] Almost
5,000 years later,

another extraordinary
piece of engineering

would underpin the success
of a major civilization

in the parched deserts
of the Middle East.

Ancient Persia.

Now Iran, a place
where art, science,

and literature flourished.

It was the heart of
the Achaemenid empire,

founded in the sixth century
BC by Cyrus The Great.

- Cyrus The Great, creates
not just an urban culture,

but also has incredibly
successful army,

constructs roads, builds
palaces, introduces coinage.

All the features that we see
really in a modern empire.

- [Narrator] By 475 BC,
it was one of the world's

dominant powers
stretching all the way

from Egypt in the west,
to India in the east,

and is recognized as one
of history's earliest

great empires.

Much of Persia was situated in
a scorching desert landscape.

Perilously dry in summer,
sometimes receiving

less than four inches
of rainfall each year.

Not even one quarter
of the global average.

Survival was far from a given,

but even with
temperatures often soaring

above 100 degrees Fahrenheit,

the Persians succeeded in
developing highly sophisticated

agricultural processes.

- They had to produce
enough food to feed the army

that supported
this great empire.

They did this by using a
type of underground channel

known as a qanat.

And this brought
the mountain waters

down into the planes
so that they could have

irrigated fields and able
to grow wide range of crops.

- [Narrator] Their
agricultural prowess

produced an abundance of food.

However, successfully
storing and preserving

this produce for
any length of time

during the intense heat of
summer, proved problematic.

Desert engineers had
to find a solution

or the population would starve.

- Preserving food in a hot
environment is a challenge.

Societies have found many
different ways of doing that.

You can dry things,
you can smoke them.

- But the person's also
siphoned off some water

in these hot, arid deserts
and turn it into ice.

- [Narrator] Producing
ice in the desert heat

may seem counterintuitive,

but it's thought that by
400 BC, ancient Persians

found a way to
capitalize on one aspect

of the harsh climate
they lived in.

- We have to remember
that in this area,

while the deserts can be
very hot during the daytime,

at nighttime, they
can drop to as low

as 20-22 degrees Fahrenheit.

- [Narrator] Their
groundbreaking invention
was a Yakhchal.

Meaning ice pit, this
conical-shaped structure

measured up to 60 feet high

and covered a deep hollow
dug in the desert sand.

The walls, up to 6.5
feet thick at the base,

were made from a local
material called sarooj.

Consisting of sand, lime, clay,

egg white, goat hair, and ash.

The domed Yakhchal, was built
next to a large shallow pond,

which was fed with
water from a qanat.

A high wall shielded
the pond from the warmth

of the low winter
sun in the daytime.

And during the colder nights,
the water would freeze.

The ice was then broken
up and transferred

into the pit below the
beehive-shaped Yakhchal.

Its thick walls helped
insulate the ice

from the intense
heat of the desert.

And the shape of the
structure encouraged

warmer air to rise and escape
through a hole in the top.

- Studies have calculated
that of the ice made

in the winter,

probably around 80% would
still be there in the summer.

And that's an example of
incredible thermal efficiency.

- [Narrator]
Remarkably effective,

the Yakhchal system
could produce ice

on an almost industrial scale.

- These could be
very sophisticated

and actually very
large structures.

And some people have
estimated they could store

the equivalent of about 3
million modern ice cubes.

- [Narrator] As well as
helping to preserve food,

ice could also be used to
chill desserts, like sherbet.

- The primary use
of the ice I'm sure,

is for keeping food fresh
and cool in the summer.

And if you are very
rich and powerful,

you might also
take a block of ice

and use it to cool down
part of your house,

as sort of early
air conditioning.

- [Narrator] There are a rare
few surviving Yakhchals today.

Over the centuries,
most were eroded

by destructive desert storms.

But this ancient technology
allowed the Persians

to prosper and survive in
the desert for centuries,

making it a true
marvel of engineering.

- Their genius was
to bring together

what we now understand
through physics,

but they must have known
through practical knowledge

about how to create ice, how
to control thermal currents,

how to insulate buildings.

They brought all
together to construct

these incredible buildings.

- So when we think of the
kingdoms and empires of Persia,

we might think of the
great palace buildings,

and rock cutter scriptions,

hidden marvels like
these Yakhchals,

actually underpin
and make possible

the day-to-day living
that made the empires

and the civilizations
exist and thrive.

- [Narrator] Throughout history,

the clever management
of natural resources

has been key to the
success or failure

of people's and powers.

And almost 1,000
years after the birth

of the Yakhchal in Persia,

another major civilization
beat the odds to provide water

to its citizens and build
one of the greatest empires

the world has ever known.

[tranquil music]

Istanbul, Turkey's largest city.

Today, the economic,
cultural and historic hub

of this vast country.

But for centuries, it was
known as Constantinople,

and was at the very center

of the longest lasting
medieval power,

the Byzantine empire.

Holding sway from the fourth
to the 15th centuries,

the empire was at its
largest in the sixth century,

when it stretched from
Italy and the Balkans,

to Turkey through North Africa,

the Middle East
and Southern Spain.

At its heart was a
bustling metropolis

with a population of up
to half a million people.

- Constantinople is
located at the point

in which Europe meets Asia.

Is literally the place
in which the trade routes

east and west converge.

- Location is everything
for an ancient city.

And it was a point through
which great caravans

of wealth and trade flowed,

it's in a very strategically
significant location.

- [Narrator] Constantinople
also had a natural harbor,

and it soon became a busy
and prosperous port city.

But there was one crucial
downside to its prime location.

- It's surrounded by water,
but it's surrounded by sea.

You can't drink it.

And it's an area with harsh
winters with dry summers.

- Getting hold of fresh water

and having a constant
supply of fresh water,

that posed a problem for a city

that was really looking to grow.

- [Narrator] Their solution
was to build aqueducts,

lots of them.

By the middle of
the fifth century,

they had constructed
a system measuring

over 260 miles that delivered
fresh water to the city.

But despite this
substantial infrastructure,

the city's water supply
continued to run dry

in the hot summer months.

- So the solution, when
you've got just seasonal water

coming into your city,

was to build some
form of storage.

And they did this
through systems,

huge underground storage pits,

lined to keep fresh water
clean so that they had access

to it throughout the
course of the whole year.

- [Narrator] Fed by aqueducts,

more than 200 subterranean
sisters existed across the city.

Even some of the smallest
could hold a body of water

weighing more than 10 tons.

But there was one hidden
beneath the metropolis,

which out-shone all the others
in both scale and beauty.

The Basilica Cistern.

- It's an extraordinary
place to visit.

You go down these
little steps underground

and there's that "wow" moment

when you see this
forest of columns.

It's more the experience
of a cathedral

than it is of a cistern.

- [Narrator] Built
around 532 AD,

the Basilica Cistern
measures 450 by 210 feet,

and could hold over 20
million gallons of water.

But that enormous
capacity presented
significant challenges.

- And it has to withstand
the enormous weight

or pressure that that
volume of water will exert

on the walls of the system.

- [Narrator] 25-foot thick
walls countered this pressure.

While the roof is supported
using 336 marble columns,

each up to 30 feet tall.

- Not only was it able to
hold up this enormous bulk

of water, but the columns
themselves supported a vaults,

which then supported a
considerable thickness

of ground above.

But when you look at
the individual columns,

you realize that every
single one of them

is slightly different.

- [Narrator] The most
spectacular are carved

with a Medusa's head.

Their origin is unknown,
but they're thought

to have been built
from materials

from destroyed Roman cities
and brought in by sea.

- And incredibly, it
carried on being used

over a thousand years
as a functioning system,

without any need for repair.

- [Narrator] Built
close to the palace

of the Byzantine rulers,

it's likely that the water
from the Basilica Cistern

was used by the city's elite.

A clue perhaps to just
why so much effort

was put into this
largely hidden structure.

- You could be walking
around the street,

you've just come out of the
great Hagia Sophia next door,

and little do you know
that actually hidden

below your feet, is
an equally impressive

engineering marvel.

- And without it,
Constantinople,

which was the capital
of this great empire,

one of the most
important civilizations

in this part of the world,

would not have been
able to function.

- [Narrator] The impressive
columns of the Basilica Cistern

carried the weight of
the city above them,

supports of a very
different kind,

underpins some of the
most extraordinary

contemporary
structures ever built.

Despite today's
exponential growth

in green and renewable
forms of energy,

oil and gas production
remain at the heart

of the world's energy supply.

Offshore drilling accounts
for around 30% of production.

And there are more than
12,000 oil and gas rigs

in oceans across the globe.

Often positioned in the center
of hostile seas and oceans,

anchoring these colossal
structures to the sea bed

called for some very
innovative engineering.

- Exploring for oil
and gas in the open sea

is incredibly challenging. The
environment is treacherous.

There's wind, there's
rain, there's waves,

there's the ocean swell, and
if you don't get it right,

there could be
catastrophic failure.

- We think we've
experienced storms on land,

but the force of a marine gale

is something entirely different.

Whatever tries to remain static,

those forces will try to
move and can even destroy.

- [Narrator] The North Sea.

Covering an area of
220,000 square miles

and hemmed in by Great
Britain to the west,

Continental Europe to the south,

and Scandinavia to the east.

184 offshore rigs
drill for oil and gas

in this region alone.

And 50 miles off the
west coast of Norway,

lies one of the most impressive,

the Troll A gas platform.

At over 1,500 feet in height,

it stands taller than the
Empire State Building,

making it one of the world's
largest gas platforms.

This is an astounding structure,

two thirds of which is
below the waterline.

And the story of
its construction

is a marvel of
hidden engineering.

- When they were
building the Troll A,

they faced numerous
engineering challenges.

Firstly, the legs had to reach
almost a thousand feet down

if they were going
to touch the sea bed.

At the top of these legs,

they had to withstand
battering by waves.

But at the bottom,

there was pressure of 500
pounds per square inch.

- [Narrator] Because of
this significant pressure,

choosing the right material
with which to construct the legs

was crucial to the
survival of the platform

and the often raging waters.

- Their solution was to
reinforce the concrete

with steel girders, which
allowed it to withstand

a bending motion
whilst also retaining

that inherent strength.

- [Narrator] One
challenge overcome,

engineers face the next;

attaching the legs to
the rig's platform.

Assembly in the
treacherous open sea

would've been impossible.

So the sections were joined in
the calmer waters of a fjord.

- An extraordinary engineering
achievement up to now,

but the best was yet to come.

They floated it
across the North Sea

until it was into position.

A really extraordinary
achievement.

It's the tallest structure that
has ever been moved by man.

- [Narrator] Upon reaching
its final position,

the structure was
sunk to the point

where the legs
touched the sea floor.

- But once it was there,
how is it fixed in place?

How do you make
this thing immovable

against the force of the ocean?

- [Narrator] When the
hollow concrete legs

are ballasted with water, the
entire structure weighs more

than the Golden Gate Bridge.

But even this enormous
weight wasn't enough

to fix the rig securely
to the sea bed.

So engineers came up with an
extraordinary hidden solution

that took advantage
of discoveries

in the power of air
pressure made more

than 350 years ago by German
inventor, Otto von Guericke.

- They were fixed to the seabed,

not with a mechanical fixing,

but through using suction.

Now, if you think of how
you have a glass of water,

and you pull it out of a
basin or a bath, for example,

you can feel the force trying
to pull it back down again.

And that's the
principle used here,

just magnified many times over.

- [Narrator] An ocean
bottom fastener,

known as a vacuum
anchor, breathed new life

into a century's old idea.

At the base of the rig's legs,

there are a series of
130-foot cylindrical-shaped

vacuum anchors with an open
end facing the sea floor.

A valve at the top of
each anchor is opened

allowing the enclosed
water and gases to escape

as the anchor is
sunk into the mud.

The valves are then closed.

And whenever the motion
of the sea applies

a lifting or sideways
force to the legs,

the vacuum increases
inside the anchors

effectively sucking
them to the floor

and securing the entire rig.

- None of us will ever
see this system working.

It's a piece of hidden
engineering, a leap of logic,

a piece of genius operating a
thousand feet under the waves.

- [Narrator] The
Troll A gas platform

has been in
operation since 1996,

and has endured the impact
of 2.5 million waves a year.

Some up to 98 feet
high, and has stood firm

against the power of
hurricane force winds

in excess of 100 miles per hour.

- This isn't just one
engineering achievement,

it's a whole series of
engineering achievements.

Each one of which
almost defies belief.

- [Narrator] Throughout history,

some of the most stunning
architectural achievements

have been underpinned
by a hidden piece

of inspired engineering.

And one of these
pivotal innovations

came in the third century AD,

when Persia the then most
powerful empire in Asia,

began a brave new
chapter in its history.

The birth of the
Sasanian dynasty.

- The Sasanians were incredible.

They're contemporary really
with the Roman empire,

though an Eastern version of it.

- From the third to
the seventh centuries,

they saw massive achievements,
both in urban development,

but also architecture
and construction.

- [Narrator] And one of
the most iconic features

of their architectural style

was a feature borrowed
from the Romans.

The dome.

- Sasanians took the
Roman form of the dome

and developed it and
made it their own.

And you can see why they did it.

They found it particularly
suited to religious buildings,

because for them it was
a kind of perfection.

It was a divine form
because it emulated

the sphere of the skies.

- [Narrator]
Visually impressive,

the dome is also an
extraordinary piece
of engineering.

Its spherical vault is
entirely self-supporting,

allowing it to span large areas

without the use of
columns or beams

to create an open space below.

- All of the weight
and the forces

travel evenly through
the depth of the dome

onto the structure
that supports them.

So they hold their own weight.

- [Narrator] Adding a dome
to a circular building,

is relatively straightforward.

As the forces are
distributed evenly

through the structure below.

But ever the innovators,

the Sasanians wanted to add
them to square buildings too,

but it presented both their
architects and engineers

with significant challenges.

- But immediately,
you want to put a dome

over a square or
rectangular building,

the dome is exerting forces
on the middle of the walls.

While at the corners,

the dome remains
completely unsupported.

- [Narrator] So ancient
engineers needed to find a way

to cap buildings with
substantial domes

in a way that wouldn't cause

the entire structure
to collapse.

- What you need is something
that can transform the load

coming through the dome
and distribute it in a way

more evenly down to the
rectangular structure.

- [Narrator] The solution
that the ancient Sasanians

came up with, was an innovative,

and rarely celebrated
piece of engineering.

- Marrying up a square
room to a round dome

was solved through squinches.

- [Narrator] To distribute
the dome's weight

evenly through the base,
squinches are shaped.

Transitionary
features were built

across the interior
corners of the building.

This transformed the
square, or rectangular shape

of the top of the
structure, into an octagon.

Meaning the forces created
by the weight of the dome,

were distributed more evenly

through the walls
supporting it below.

- The squinch sounds
like a technicality,

but it's a kind of
hidden technology,

because we just
take it for granted.

Without that leap of logic,

then the Persian empire
wouldn't have developed

the architecture of domes,

which is really one
of the great glories

of world culture today.

- [Narrator] One of the oldest
examples of a Persian dome

that utilizes the
squinch is found

at the palace of
Ardashir in Iran.

It was built in the
third century AD,

using cobbles
embedded in mortar.

- The Sasanians were
the experts in building

this type of domed architecture.

And shortly after the
invention of the squinch,

this area of Persia was
invaded by the Muslim armies,

who saw this fantastic
type of dome construction.

And it was then adopted almost

as the signature
architecture of Islam.

- [Narrator] And it was
during the Islamic Golden Age,

that a stunning variation
on the squinch emerged,

the muqarnas.

First appearing in
the 10th century

in Iran and North Africa, it
is a purely decorative feature.

It's complex 3D
geometric patterns

designed using little more
than compass and ruler,

were used to smooth
the visual transition

from straight walls
to domed roof.

- It is, you know,
an absolute marvel,

and without the squinch,

we would not have the
amazing domed architecture

of the Islamic world.

- [Narrator] The humble squinch,

sewed the seeds of an
architectural revolution.

And over the centuries, the
dome continued to develop.

Culminating in the construction
of what would remain

the largest cathedral in the
world for almost 1,000 years.

The Hagia Sophia in Istanbul.

The building's most
prominent dome,

achieved its
impressive dimensions

by utilizing the
successor to the squinch.

- The Byzantine empire,

they were also experimenting
with dome structures,

but there they used a
different form of stabilization

known as the pendentive.

- [Narrator] Essentially,
a spherical triangle

that serves as an arch.

This more complex
version of the squinch

provided abundant
space for decoration,

and is still in use today.

The dome remains an
intrinsic feature

of modern architecture.

And one in particular
became emblematic

of perhaps the most seismic
event in 20th century history.

In the German capital, Berlin,

an iconic building has come
to symbolize new beginnings

in the country's often
turbulent history.

And stands as a landmark
on the city skyline.

After its opening in 1894,

the Reichstag became the home

of the German Federal Parliament

during the late Imperial Period,

and through the Weimar Republic.

- Most famously of course, it
survived the second World War.

There's a very famous
photograph of Russian troops

raising a flag on
top of the building

once they'd taken Berlin.

- [Narrator] When the war
ended, Germany was split in two;

the Western half a democracy,

the Eastern, a communist state.

In the early sixties,
a wall was built

physically dividing the city.

By this time, the parliament
had already moved to Bonn,

leaving the Reichstag
with no significant role

for more than a
quarter of a century.

- As a consequence of
the division of Germany

into east and west,
this building's kind of

without function
and without purpose.

So for a building that had been
so prominent in the empire,

it had really quite an
ignominious fall from grace.

[lighthearted music]

- [Narrator] But 44 years
after the end of World War II,

came the most seismic
moment in modern history.

[people cheering]

When events unfolded, that would
change the fate of Germany,

Berlin and the Reichstag itself.

- In 1989, the Berlin
wall comes down.

And this is a really important
moment for European history,

because by October, 1990,

east and west Germany
have become reunified.

- It was a new beginning
for the country,

and it was decided that the
seat of this new democracy

would be moved to the
Reichstag in Berlin.

- [Narrator] After
decades of division,

a now reunified Germany
wanted to mark this moment

of renewal and the Reichstag,

originally built with a
dome that was destroyed

by fire in the 1930s,
was to be restored

to its former glory,

but with a
state-of-the-art edition.

- So what they decided
to do is to put in place

a new glass dome.

And this was seen
as a sort of symbol

of the new transparent democracy

that Germany was to
enjoy from then on in.

- [Narrator] The new dome
was 131 feet in diameter

and 77 feet high.

But adding a modern
structure to an old building,

required innovative
engineering solutions.

- When you're retrofitting
a historic building

and adding new parts, you've
got all sorts of problems,

not just of design,
but of construction.

- [Narrator] Just as
the Sasanians had done

in centuries passed, the
engineers of the Reichstag dome

used a transitional feature
called a box girder,

on the top of the building.

24 art-shaped steel
ribs were then added

to the circular girder to
form the shape of the dome.

The ribs house hinges,
supporting pedestrian ramps,

which afford visitors a 360
degree vista of the city below.

As architecturally
striking as it is,

the dome still had one
major practical issue.

- The problem is, is you create
a big iconic dome like this,

but you are also
creating a glasshouse.

And glasshouse means heat.

So you also have to have an
incredibly innovative system

of circulating air around it,

just so people inside
it don't cook off.

- There were two solutions to
keep the building below cool.

Firstly, there is
this solar shade,

which electronically tracks
the movement of the sun

to block direct sunlight.

And secondly, there are gaps
in the glass panes of the dome,

which allows rising heat to
escape. So natural ventilation.

- [Narrator] The new Reichstag
dome was completed in 1999,

and the German Parliament
took a permanent residence

in the building in
September of that year.

- It's a beautiful,
modern reinterpretation

of a fantastic
engineering design.

- [Narrator] An exquisitely
engineered juxtaposition,

the dome has become one of
the most symbolic structures

in all of Germany

Today, discoveries
continue to be made,

which shed new light
on concealed innovation

in ancient technologies,

which culminated in
extraordinary engineering.

In 12th century,
Ethiopia, King Lalibela

ordered his people
to construct a series

of 11-below ground churches,

all literally hued
from solid basalt.

In the meso-American
city of Teotihuacan,

in the first century AD,

the massive Pyramid of the Sun

was constructed as a
monument to the environment

that surrounded its people
using little more than earth.

While in the 12th century,

high in the Andes
mountains of Peru,

the Inca were
establishing themselves

as one of the great south
American civilizations.

But in order to farm, often
at heights over 10,000 feet,

the Inca constructed two
and a half million acres

of terraces.

And at one location in Moray,
the temperature difference

between the top
and bottom levels

can be as much as 27
degrees Fahrenheit,

leading to an
astonishing conclusion.

- The identification of these
different micro climates

has led researchers to believe
that the Moray terraces

are actually an ancient
agricultural research station.

- So you could test
what crops would grow

at what level of altitude,

and this enabled the
Inca to experiment

with all types of crops,
and to really expand

their range of
agricultural development.

- [Narrator] Over 1,500
years prior to the end

of the Inca empire,

on the other side of the world,

Greecian engineers had found
a completely different purpose

for another circular form
within the natural landscape.

[exciting music]

The ancient Greeks,
brilliant mathematicians,

artists, and philosophers.

And creators of one of the
most impressive buildings

of antiquity,

the Parthenon.

Constructed in the
fifth century BC

to honor Athena, the
Greek goddess of war,

its marble columns still
dominate the Athens skyline

almost two and a half
thousand years later.

But it's not the only work
of Greek architectural genius

to have survived
the ravages of time.

Southwest of Athens,
lies the Peloponnese.

A mountainous peninsula of
more than 8,000 square miles

jutting into the
Mediterranean Sea,

and home to a marvel
of ancient engineering,

which is a feast for
both the eyes and ears.

The Theater of Epidaurus.

- The ancient Greeks love drama.

They invented tragic
drama, comic drama.

So wherever the Greeks
went, they built theaters.

I think the first impression
you'd get as a visitor

is how beautiful
this building is.

It has a sort of
grace and symmetry

and it's part of a very
beautiful natural landscape.

- [Narrator] Constructed
in the fourth century BC,

the Theatre of Epidaurus could
seat up to 14,000 people,

and was used for performances
for over 500 years.

But it's not just its
incredible architecture

that sets it apart.

- A hidden feature
of this theater

is how well it's
engineered for sound.

- You can hear everything
that happens on stage

with immense clarity,
wherever you are sitting down.

- [Narrator] Recent
tests have shown

that sound at the theater
can be heard almost perfectly

at a distance of 195
feet from the stage.

But delivering such
exquisite acoustics

is a delicately
engineered balancing act.

When sound is generated,

it propagates in waves from
its source to the listener.

The first waves are
called direct sound.

Sound waves that bounce off
surrounding surfaces once,

and reach the listener
fractionally later,

are called first reflections.

And finally, the sounds that
bounce off multiple surfaces,

usually walls and the ceiling,

reach the listener last and
are called late reverberations.

Good acoustics depends on
getting the combination

of direct sound,
first reflections,

and late reverberations
just right.

- You have to keep in mind
that Theatre of Epidaurus

is an open structure.

It doesn't have a ceiling.

So you only have direct sound,

and some early reflections,
no late reverberation.

You only have two of the three
elements for good acoustics.

And yet, it still manages
to have great acoustics.

- [Narrator] So how did the
architects of Ancient Greece+

engineer near-perfect
sound so long ago?

- The most effective way
to ensure that sound reach

from the stage to the
audience is to channel

and reflect that
sound using the shape

of the theater building itself.

This concave bowl of seats
in a fan-shaped array

heading up the hillside,
helps to funnel

and direct the sound and keep
it within the audience area.

- Because of that, the
audience had a direct sideline

to the actors on stage.

And so the sound
was unobstructed

in its propagation from
stage to the audience.

- [Narrator] In 2007,

researchers from the Georgia
Institute of Technology,

pinpointed another design
feature that may have helped

its architects achieve
such amazing acoustics.

- They believe that the
very regular pattern

of the seats and the
specific distance

between one row and the other,

act as a acoustic filter.

- [Narrator] Studies concluded

that the seats filter
low frequencies,

thereby increasing the
relative proportion

of high frequencies,
on which hearing

the human voice
clearly, is dependent.

- This acoustic filtering
effect makes sounds clearer

and more intelligible.

And this is the stunning example
of acoustical engineering.

- [Narrator] There can be
little doubt that ancient Greeks

created a beautiful theater,

and an almost acoustically
perfect performance space

at Epidaurus.

But where the hidden
marvels of its design

an exquisite feed
of engineering, or
a happy accident?

- Whether they understood
the signs of acoustics

as we do are rather down,

but they knew what worked,
and they had enough experience

and practical knowhow to ensure

that the way they
built their theaters

suited the need to
hear very clearly

what the actors were saying.

- [Narrator] Whether
intentional or accidental,

the theater's combination
of architectural beauty

and exceptional acoustics,

is a triumph of
ancient engineering

that influenced the
design of theaters

for centuries to come.

It's such an impressive feat,

that even world-class
architects of the modern era

have found it
difficult to replicate.

The Sydney Opera House, famed
for its groundbreaking design,

architectural innovation, and
soaring sail-shaped shells.

But hidden beneath its
world-famous facade,

is a dramatic story of
complex engineering challenges

and extraordinary solutions.

- While we marvel at these great
technological achievements,

they're often the product of
a much lesser known process

of experimentation.

Without which, these great
engineering structures,

they could not
have been created.

- [Narrator] The
Sydney Opera House

was the brainchild of Danish
architect, Joørn Utzon.

But such an ambitious project,

brought with it
considerable challenges.

Many believed his radical
design could never be built.

Incredibly, it wasn't
until two years

into the construction
of the foundations,

that Utzon finally solved
how to actually construct

the complex shape of the
buildings outer shells.

- He came up with his
solution when he realized

that all the shapes of
the sail could be created

from one piece of
geometry, a sphere.

Which meant segments
could be pre-fabricated.

- [Narrator] This avoided the
need for expensive form work

by allowing the use
of pre-cast segments,

which could be
more easily formed

because of the
ease of repetition.

Utzon's insight is known
as the spherical solution,

and is recognized as
a timeless expression

of the fusion between
design and engineering.

Despite this significant
breakthrough,

Utzon was forced to resign
halfway through construction,

due to ongoing delays
and spiraling costs.

His replacement, Peter Hall,

oversaw the
building's completion.

But Utzon's spectacular
original interior design

was never realized.

And the acoustics
in the concert hall

fell short of expectations.

- There are too many issues.

The orchestra can't hear
each other and themselves

as well as they should.

And the sound that reaches
the audience lacks power.

- The concert hall is a
space built for music.

As beautiful as the
architecture might look,

getting the acoustics
right is crucial.

- [Narrator] The beautiful,
but awkwardly shaped hall,

and it's partially
vaulted ceilings

created unwanted reverberation.

- So they installed an
array of ring shaped

hollow reflectors
hanging above the stage.

- [Narrator] Each of
these 21 reflectors

measured around six
feet in diameter.

And because of their
distinctive shape,

they became known
colloquially as the donuts.

Only ever intended to
improve the balance of sound

for the musicians in
the orchestra pit,

they weren't as
effective as hoped.

- Over decades, acoustical
engineers tweaked the design

and the arrangements of
this donut reflectors.

But in spite of the effort
they didn't work that well,

probably because the area
covered by those reflector

was not sufficient.

And also the round shape
was scattered sound too much

as opposed to
create very focused,

loud reflections on stage.

- [Narrator] The ongoing
problem of poor acoustics

for the audience remained
even harder to solve.

- The main issue is that
the lightweight structure

of the building is not
capable of containing

low frequencies in its interior.

Therefore, the reverberation
time at low frequencies

is very poor.

As a consequence of that,

the sound of the orchestra
doesn't sound as rich

and full as it should.

- [Narrator] In an attempt to
finally resolve the issues,

in 2020, an extensive two-year

multimillion-dollar
refurbishment of the hall began.

This saw the famous
donuts removed

and replaced with paddle-shaped
fiberglass reflectors.

- This will improve
early reflection

and ensure that musicians can
hear than self quite clearly.

And also the audience will
receive much greater amount

of early reflection and that
will improve clarity of sound.

- [Narrator] Newly
designed wooden reflectors

were also installed
on the walls,

as well as extensive
adjustable acoustic drapery.

- This in combination
with a state-of-the-art

electro-acoustic system,
will enable the concert hall

to be quickly adapted to
different genres of music,

from amplified
music to classical.

- [Narrator] To
celebrate 50 years

after it first opened its doors,

the stunning architecture
of the Sydney Opera House's

exterior may finally be matched
by world-class acoustics

inside its concert hall.

Through the ages, our
ancestors' astonishing drive

to innovate has propelled
the march of history.

And seeing humankind develop
from hunter gatherers

to establishing
immense civilizations.

- The human story is
one that is indexed

incredibly closely to
feats of engineering

as we've confronted the
various challenges of the day.

- [Narrator] But often, some
of the incredible technology

that contributed to the
success of their creations

remains hidden or buried
by the sands of time.

- So much ancient engineering
is already known about,

but in reality, it's just
the tip from iceberg.

- [Narrator] What other
jaw-dropping engineering

marvels lie hidden?

Only time will tell.

- No doubt will continue
to be surprised and amazed.

[exalted music]