All language subtitles for How.Did.They.Build.That.2021.S02E08.Breakthroughs.and.Bridges.1080p.WEB.h264-CAFFEiNE_track3_[eng]

[Male Narrator]
What happens when 41 stories

of radically futuristic design
reshapes one of the world's most

recognizable and historic
skylines?

I was described as
public enemy number one.

[Narrator] How do you build
a record-breaking bridge

without foundations?

These are the kinds of problems
that keep bridge engineers

up at night.

[Narrator] And where do you
begin with a gravity defying

cloud of glass and steel,

described as
architectural chaos?

[Wolf] We can build everything

and not in the stupid way
of doing boxes.

[music]

[Narrator] This is the
age of the extraordinary.

[Haley] It's like one of those
insect eating plants,

only enormous and white.

[Narrator] Where ingenious
engineers have unleashed

unchecked creativity.

Now their secrets are revealed.

As we discover the inside
stories of their construction.

This is an incredible feat of
planning and engineering.

[Narrator]
To try and understand,

"How Did They Build That?"

For our first building we're
heading to England where

in 2001, one of the world's most
celebrated architects

set out to create
an extraordinary building

that would change the
London skyline forever.

With the address 30 St. Mary Axe

it clearly needed a snappy
nickname like the rocket.

No, no, no.
The cigar.

No Jay.
I know what we'll call it.

The Gherkin.

[Narrator] The City of London.

Home to the
Bank of England since 1694

and a financial
powerhouse ever since.

It's known for
its traditional values

and until 20 odd years ago,
its traditional architecture.

It's really hard to imagine now,

but apart from
the Lloyds building

that financial district
of London was architecturally

really quite dull.

[Narrator] Then at the very end
of the last century,

the opportunity arose
for a visionary architect

to change all that

with a building that would drag
the city kicking and screaming

into a new millennium.

No one has ever seen
a building this shape

and size anywhere in the world.

[Narrator] 41 stories of
cutting-edge glass and steel

that was ruffling feathers
before it was even

off the drawing board.

[Lord Foster] In the opinion
page of a prominent newspaper,

I was described as
public enemy number one.

[Narrator] An extraordinary
concept that forced engineers

to use techniques
never before tried

in a building of this kind.

This is 30 St Mary Axe.

Controversial, iconic
and one of a kind.

It transformed the
skyline of London forever

and challenged engineers
to redefine the possible.

So how did they build it?

It's 1992, and a terrorist
attack in the heart of the

city of London provides an
unlikely catalyst for change.

A bomb is set off
by the provisional

Irish Republican Army

killing three people
and injuring 91 others.

It damages the Baltic Exchange,

a trading hall that had
been at the heart of the city

for nearly 100 years.

The decision is taken
to allow something

much bigger in its place.

Norman Foster, one of the
world's most famous architects.

Responsible for the
Millau viaduct in France,

and the Hearst Tower
in New York,

takes up the challenge of
redefining London's skyline.

[Lord Foster] Can it give
something back to the city

of which it's a part?

In each of these buildings.
They interact with the city.

They try to give
something back to the public,

as well as creating
something very, very special

for the private spaces
within the building.

[Narrator] What Lord Foster has
planned for the site

takes special
to a whole new level.

A 180-meter tall,
57-meter-wide tower

completely in the round.

In order to reduce
the impact at the ground,

it will get wider as it goes up

before being topped
with a dome of glass.

An interlocking gridshell
of two-story-high steel columns

will interconnect
at 18 different points

every other floor.

It will then be covered
in an intricate skin

made up of 7,492 panes of glass.

In an incredibly
high-tech world,

here windows will simply open
and close with the weather.

The passive cooling system
will circulate air

through the building,

cutting down
on air conditioning,

and giving it some
seriously green credentials.

The Gherkin was
an object of derision.

I think the name Gherkin
originally was hostile.

In the opinion page
of a prominent newspaper,

I was described as
public enemy number one.

[Narrator] Despite the press
being against the building,

in 2000 and with
some trepidation,

the planning committee grants
permission to go ahead.

A year later,

the construction
teams break ground.

Arriving here and seeing the

enormity of the task
was inspiring.

You really felt like
you were getting involved

with something that was going
to be out of this world.

[Narrator] The first challenge
is to lay the foundations.

[Ellie] The base of the Gherkin
is remarkably small,

but because it
swells as it rises,

what you get is a very large
building with a very small

ground-level impact.

[Narrator] It also creates
a serious challenge

because it means the entire
weight of the large building

is concentrated
onto the small footprint.

Unable to spread the weight out,

the engineers have to create
some heavy-duty foundations to

keep the building from sinking
into the soft London clay.

Here you want to make sure
foundation's sound.

People think that the building,

that the bits they see
of the building is complicated.

There's an awful lot
in the ground

that's similarly complicated
that you will never see.

[Narrator] The team
starts by drilling piles.

These underground columns
measuring about

five and a half miles in total
will hold the tower up.

Each has to be engineered to
within an inch of its life.

The load was designed
for 117 thousand tons.

We drilled 333 piles
into the ground.

Collectively,
that's nine kilometres

of straight shaft digging.

The London clay, it gets harder
the further you go down.

And when I say hard,

it's like steel when
you hit down on the bottom.

It is that hard.

[Narrator]
With the piles drilled,

the team plans to finish the
foundations with a massive

eight-feet deep concrete slab

connecting all
333 piles together.

It's absolutely crucial
that the entire slab

cures at the same time.

No mean feat when you're
pouring this much concrete.

You could end up with
the bottom of the pile cap

curing before the top
and it's not bonded together.

And that's not good.

[Narrator] The entire pour
has to happen in one go.

And the concrete is specially
treated to make sure none of it

cures till the last lot goes in.

There's an additive added to it,

which made sure that the
first lot that got poured didn't

harden until the top part has.

So the whole lot
could go off as one piece.

We had three concrete pumps,
delivery pumps

situated on three of the corners

and we had 27 concrete trucks
on turn around,

bringing this concrete in

from three different depots
around London.

So it was a military maneuver
that took just over 12 hours

of one continuous pour.

[Narrator]
The crew pours over 63,000

cubic feet of concrete.

But with meticulous planning,
it goes without a hitch.

Now with a solid base
to build from,

the engineers get to work
on the complex steel structure

that will hold the building up.

It's known as a diagrid.

The diagrid frame
is a network of triangles,

which are also hugely
strong and efficient,

but it also gives the building

that unmistakable
trademark skin.

[Lord Foster] The Gherkin and
the Hearst Building in New York,

when you look at them, they both
have triangulated structures.

Why? Because a triangulated
structure is inherently

more rigid with less material.

[Narrator] Constructing it
is the next challenge

because this is one
of the first times

a diagrid structure has been
used to build a skyscraper.

[Rob Harrison] Everybody here
really felt this is

the proper start to the project.

Everybody around the city,
anybody who was coming past

was going to view this building
rising from the ground.

[Narrator] The plan is to start
with the core of the building,

which will act like the spine.

The steel diagrid structure
will be built around it

and connected back to the core
through a series of nodes

in the steel frame,
like the spokes on a bicycle.

All watched carefully
by the building's detractors.

[Paul Davies] The core itself
was always six floors above

building the outside structure.

There were 18 of these
frames per floor going around

before the next set come on top.

[Narrator] Then,
as the building gets higher,

something strange
starts to happen

that threatens
the entire project.

[Paul Davies] Our engineering
team started noticing

things weren't exactly
where they should have been.

[music]

[Narrator] Next, the teams have
to find out what's going on.

[Narrator] It's 2001,
and in London, England,

work is underway to build a
revolutionary new skyscraper,

but it's hit a major problem.

For some unknown reason,
the structure is moving.

They have to find out why.

[Paul Davies] Our engineering
team started noticing

a constant pattern of errors.

They did something
in the afternoon,

the following morning
when they checked it again,

things were out of where they...
Out of plum.

[Narrator] After some
serious detective work,

the team discovers the culprit.

London's famously
changeable weather.

Steel changing its dimensions
due to weather is a really

big challenge in construction.

[Narrator]
When steel gets hot, it expands.

In cold, it contracts.

And that is exactly
what's happening here.

In summer, in London it can
be freezing cold one day

and then the next day
you have blistering heat.

So the challenge becomes how do
you calculate for temperatures

that you can't predict?

[Paul] The only way
we could correct it

was getting the engineers
to transfer working at night

when it was cold.

And by and large,
not very windy.

[Narrator]
And by doing just that,

they're able to get
constant measurements

that overcome the problem.

But the challenges
don't end there

because the engineers need to
somehow counteract the building

moving under its own weight.

You've got the two and a half
thousand tons worth of steel,

which gradually gets loaded.
Each floor adds more weight.

That weight obviously
compresses down.

And it's a bit like overeating.
Your stomach comes out, yeah?

And it's exactly the same
with this structure.

As the weight comes on

the circumference
of the building grew.

And each level was designed
to settle by 40mm.

It did that to perfection.

[Narrator]
The frame is designed with an

extra bolt on each connection,
so floor by floor,

once the building
finishes settling,

the construction crews
tighten them,

creating a completely
rigid structure.

[Corina] The engineers who
designed these steel frames

are getting so good
at predicting deflection.

They can keep tolerance
to a minimum

and so get narrower gaps in
framework and the facades,

so you end up
with a slicker finish.

[music]

[Narrator] The next challenge
is getting that perfect finish

using almost 80,000 square feet
of glass.

To pull it off, the team turns
to what is at the time,

a revolutionary idea.

They use cutting-edge computer
technology for the design.

The result is a pattern
of 7,492 panes of glass,

but they fit without a hitch.

And somewhat strangely
in a building

that's all about its curves,

7,491 of them are actually flat.

So the very last piece of glass
to go in is the lens at the top

of the building, which was
2.4 meters in diameter,

250 kilograms.

And the actual capping
piece of glass was lifted up

by a tower crane with the rope
access guides going around it,

installing the pressure plates
that hold it down.

[Narrator] This building is
different in so many ways

from those that have
come before it

and most that have been
built since.

[Lord Foster]
It's tighter at the base.

It swells out in the middle and
it reaches a point in the sky,

which unusually is not devoted
to mechanical equipment.

[Narrator] Most buildings have
their air-conditioning units

on the roof.

The reason they sit
outside on a roof,

it's so that they get
free ventilation to them.

So bringing that inside
the building was a challenge.

[Narrator]
In order to pull this off,

Lord Foster needs a system
of cooling the building

that does not completely
rely on air conditioning.

It's genius is
in its simplicity.

There's six triangular light
wells on every floor.

There's four windows at the end
of that light well.

They're triangular windows.

And they open up when the
weather conditions are right.

[Narrator] If the building
is getting too hot,

the automated glass
hatches open up.

And if it's cold outside,
the windows close

to retain the heat.

The pinecone,
which opens and closes

according to the weather,

it's pulling air through the
lungs of the building.

It's making it
more healthy, fresher

and dramatically reducing
the amount of energy.

Up to 50% less energy compared

with a convential building.

[Narrator] In December 2003,
the Gherkin is finally complete.

Stunning on the outside

and inside, thanks to reducing
the need for air conditioning,

there's a restaurant rather
than a plant room at the top.

[Lord Foster]
In that sense it's almost unique

because the top of the building
is about the panaroma

of the city, the region.

It's for the people.
It's not for the machinery.

[Ellie] That continuous,
glazed domed roof

with those 360 views,

it is an exquisite design vision

only made possible
by brilliant engineers.

[Paul] My personal feelings
when we actually completed

was one of elation, pride.

It was the best four years
of my life.

It's given an awful lot back
to the city of London.

[Rob] Anybody who was
involved in this building has

a huge amount of pride in it.

And its legacy will withstand

and will retain for many,
many decades to come.

[Narrator]
Born out of an atrocity,

and vilified
before it was built,

30 St. Mary Axe has become a
symbol of a new city of London.

A building that is as clever
as it is beautiful.

A structure that challenged
traditional thinking.

And one that has
changed the skyline

for a very long time to come.

[music]

If I said I was gonna build
a road bridge across a lake

a mile and a half wide,

but instead of securing
the bridge to the riverbed

and supporting it
with huge towers,

it would just float
on the lake's surface

on 77 concrete pads.

You'd probably think
that was a crazy idea.

The thing is, in Seattle,

one thing they really love
is crazy ideas.

[Narrator] And on the surface,
that's exactly how it sounds.

The problem was that Seattle
desperately needed a new bridge

to get people in
and out of the city.

But Lake Washington is so deep
and the lake bed so soft,

that traditional bridge building
is a no-no.

So they decided to construct
the world's longest

and widest floating bridge.

It had to hold up a rigid road,

yet somehow move
with the natural forces

of the water below.

Building it pushed engineers

into some seriously
choppy waters.

These are the kinds of problems
that keep bridge engineers

up at night.

[Narrator] They had to create a
mega drydock from scratch

where they could
construct the 77 enormous

concrete floating pontoons.

Any imperfection could
lead to the pontoon sinking

to the bottom
of Lake Washington.

[Narrator] Every piece had
to be transported over 200 miles

through the Pacific Ocean.

This is the Evergreen Point
Floating Bridge,

a record breaker that took world
class engineering to realize.

So, how did they build it?

[Narrator] It's 1997,
and in the pacific northwest,

the city of Seattle is
growing bigger by the day.

A tech boom is attracting
more and more people

making it one of the fastest
growing cities in the US.

But its infrastructure
is starting to creak.

And in particular,

an old bridge
over Lake Washington,

a vital link to the city
built in the 60's,

which can't cope
with the volume of traffic.

There are regular
backups for miles

and it's literally cracking
under the weight.

With the existing bridge
at the end of its life,

the designers find themselves
in a race to replace it.

The weather, the traffic,
the levels of the lake changing.

These are the kinds of problems
that keep bridge engineers

awake at night.

[Narrator] Building this
bridge over Lake Washington

poses a unique set
of challenges.

Not only will it have
to span over 1.4 miles,

but solid ground is hundreds
of feet below the surface.

Don Oats is one
of the design managers

tasked with coming up
with solutions.

[Don] Lake Washington
is a unique lake.

It's very deep. It's about
200 feet to the mud line,

because of the volcanic
eruptions it's actually filled

with very, very soft soil
to a depth of about 80 feet.

And then below that,
you'd have to excavate down

about another 100 feet
to be able to get to dirt

that you could actually build
a structural foundation on.

[Nehemiah] If you went with the
traditional suspension bridge

like, say,
the Golden Gate Bridge,

you would end up with towers
that are about 400 feet tall

before they even
got out of the water.

[Corina] Then add
another 600 to support

the suspension bridge roadway,

that's a 1,000-foot tall tower.

Not gonna happen.

[Narrator] The team takes
inspiration from the old bridge

and decides to create a new
supersized floating bridge.

This new bridge will have
an extra four lanes

and room to expand
to take a light railway

if it needs it in the future.

The road will be elevated
above the pontoons

and cushioned with shock
absorbers to stop the vibrations

from cracking the structure.

And everything will be
balanced on top

of 77 floating concrete pontoons
anchored to the lake bed below.

Now the engineers just need

to float hundreds of thousands
of tons of concrete.

Making something that
floats out of concrete

may seem quite unlikely,

but actually it's
just simple physics.

Imagine this is concrete.

Guess what?
It sinks.

But if I take the same
amount of concrete

and shape it into a cup.

This time, it floats.

[Narrator] Even though
making the enormous concrete

bridge float is possible,

constructing the giant
pontoons creates its

own set of challenges.

Firstly, they need a massive
dry dock in order to build them.

A dry dock helps you
build a boat

or in this case, our pontoon

in what is essentially
a giant empty bathtub.

When the pontoon
is ready to float,

the dry dock is flooded
by lowering a massive gate

and the pontoon can float out.

[Don] We figured out
it needed a basin about

900 feet long by 200 feet wide.

[Narrator] It's a huge area,

roughly the size
of six soccer fields.

Which is not exactly easy to
come by in a busy bustling city.

In the end, the team finds
a disused lumber yard

80 miles away in the
coastal town of Aberdeen.

Not exactly local,

it proves to be one
of the few places available

to build the enormous dry dock.

Overseeing construction
of the pontoons

and the brand new $367 million
dry dock is Phil Wallace.

This is our 55-acre
casting basin that we had

down in Aberdeen, Washington.

This basin was built,
so we could cast six pontoons.

So four along two pontoons

and two of the auxiliaries
in the back.

We put in a gate in this area
here to allow the pontoons

to float out.

We had over 600 employees
working there

at different times a day,
working days and nights.

[Narrator]
With the dry dock ready,

work starts on
building the pontoons,

which will be cast using
over half a billion pounds

of concrete.

To make the pontoons,
the engineers built a

massive mold known as formwork.

Then they started pumping
in concrete to fill it.

This is a critical stage
on any build.

[Ellie] Any imperfection
could lead to a fault,

then a fracture.

And then ultimately,

to the pontoon sinking to the
bottom of Lake Washington.

They're like 200 tons a piece.
Everything is big.

The most critical pour that goes
in is the wall form pour,

the exterior wall
of the pontoon.

In that pour,

you need to make sure you
have a good joint at the bottom.

[Narrator]
Although the team strives

to make each pontoon perfect,

they're designed with the
worst-case scenario in mind.

Instead of being a
single large space,

they're divided
into sealed compartments,

so if one leaks,

the others can
still do their job.

So we're currently inside one
of the larger pontoon cells,

and you see hatches
to the adjacent cells.

All of these
hatches are watertight.

So keeps the cells separated
in case there's any water

entering any of these cells.

So all of that is connected to
the pontoon-monitoring system.

So there's alarms trigger

in case any of these cells
need to be pumped out.

[Narrator] It takes months,
but eventually,

the pontoons are completed
and moored at a nearby harbor.

But before they can be
transported to Seattle,

the engineers need to create
a system for anchoring them

in place once
they get them there.

One that can cope
with the varied lake bed

and the forces of the water.

[Don] There were three different
types of anchors

for the different soil
conditions that we had.

The shaft anchor, eight-foot
diameter steel shafts

that go into the ground filled
with concrete and a steel cage.

[Narrator] The next anchor type
is nicknamed the box of rocks.

That are literally
40 by 40 by 20 foot tall.

They look a lot like pontoons,
but they're open top.

They are 600 tons
with all the rock in them.

[Narrator] The last are
like a supersized,

traditional ship's anchor.

45 will be used on the bridge.

[Don] All the anchors
we had to test for loads

up to about 570 tons.

So it's a massive load
that these anchors can take.

[Narrator]
The pontoons are cast.

The anchors are set.

It's now time to tow them
the 260 nautical miles

around the coast
and into Lake Washington.

But this means going out
into the open sea.

Here the 360 by 75 foot
pontoons will be at the mercy

of the Pacific Ocean.

[Narrator]
In the pacific northwest,

engineers are planning
to transport massive cement

pontoons through open ocean

to construct the world's longest
floating bridge in Seattle.

You got big tractor tugs
that take them up the coast.

We didn't float them until
we knew we had a nice window

where we weren't going to
have any storm conditions.

We generally could
go four knots.

That was probably the maximum
speed those pontoons could take.

So you're out there, you know,
a couple of days in the ocean.

[Narrator] Moving each
pontoon takes around two days,

but finally the 77 are in place.

Now the engineers
face their next challenge.

Although the pontoons
are anchored,

they move with
the water of the lake.

Somehow, they have to figure out

how to fix this
constantly moving bridge

to the rest of the highway,
which is fixed on land.

[Nehemiah] Fixing the stationary
structure to a moving one

is incredibly difficult.

In this case, that structure
is floating on a lake.

All kinds of things can happen
to make that structure move.

[Don] The transition span
was one of the more complicated

pieces of infrastructure
we had to build.

The floating
infrastructure moves,

fixed structure hopefully,
does not.

And so you have to figure out
how to connect that.

[Narrator] They turn to
automotive engineering

for a solution.

We put it on what we
called a large trailer hitch.

Just like a tow hitch,
this has spherical bearings

that let the floating section of
the bridge move up and down

and side to side.

It's these that keep the bridge
from tearing itself apart.

[Narrator]
With each pontoon connected

by massive bolts and cables.

A raised roadway is added
to the top of the pontoons.

To prevent it from cracking,

the entire six lane wide road
sits on special shock absorbers.

So we're currently standing
on one of the longer,

longer channel pontoon.

This is 360 feet, so about the
length of a football field.

This makes a majority
of the foundation that's

holding up the bridge
structure above us.

You can see on
all the columns here,

there is a bearing
sitting on them,

so it allows for a little bit of
movement there in the road sway.

Those are pretty much cushions
that the roadway is sitting on.

And so along the entire bridge,
you can see there's

hundreds of these holding
up the bridge stacked

on top of all the columns.

[Narrator] Finally,
after four years,

this 1.4 mile long
record-breaking floating bridge

is in place.

And the first people
who get to use it,

are the families of the
dedicated men and women

who helped build it.

We actually had a family day
where all the workers

that had worked on the job were
invited out to walk the bridge.

So the people that
built the bridge,

actually get to see it first.

And then a couple of days later
the state had a big celebration

and over 50,000 people showed
up for that celebration.

[Don] I mean,
there were some hard times

and we went through some
really stressful events.

And some ones that
you kind of laugh at now

when you kind of think
back at them,

but there's a lot of pride
that we have from it.

[Narrator]
This simple ribbon of road

hides its importance as a marvel
of innovation and engineering.

While for locals,
it's a lifesaver,

giving them back all those hours

that would otherwise
have been spent

sitting in a traffic jam.

[music]

As in all fields of creativity,

it's easy to think that surely
by now everything possible

in architecture has been done.

I mean, there can't be any more
genuinely original ideas, right?

But back in 2001,
a call went out

to design a new museum
of science and anthropology

for the French city of Lyon.

The opinion-splitting building

which resulted was
totally unlike anything

that had gone before.

Nor has there been anything
else like it ever since.

Mold-breaking design classic
or just architectural chaos?

You decide.

[Narrator] Take one tiny spit of
reclaimed land

sitting where two rivers join.

We said we should move it.

The government said, no, no way.

[Narrator] A French city that
wanted to create a building

for which it would
be remembered.

[Corina]
A building that's a cloud

with a whirlpool in its ceiling?

Only in France.

[Narrator] And an architect with
a passion for the extraordinary,

and a hatred of the ordinary.

I basically, I hate columns.

[Narrator] And what they got
was a building so complex

that even its designers couldn't
predict the final result.

And where, from the
metallic cloud-like front

to its crystalline back,

every piece seemed more
complicated than the last.

[Marcus] Even for us architects
is how will it really look like?

[Narrator] Nicknamed the cloud,

This is the
Musée des Confluences,

a gravity-defying,
mercurial structure,

which would push both
architects and engineers

to realize the impossible.

So how did they build it?

In 2001, the rather traditional
city of Lyon

decides that it's going to bring
new life to a small,

neglected part of the city.

A thin spit of land

that was created
over 100 years ago

and sits where the Saone
and the Rhone rivers meet.

Until now,

it's been little more
than a local picnic spot,

but the city has bigger plans.

They want a centerpiece
to attract new investment

to the city on both sides
of the river.

And decide on a
new museum building

to symbolise the coming
together of the two rivers

with a meeting of minds.

Now all they need is a design.

They turn to award-winning
architect, Wolf Prix.

Whose buildings
are as extraordinary

as they are beautiful.

The Musée de Confluences
is going to be no exception.

We can build everything

and not in the stupid way
of doing boxes.

We try to liberate space.

It is not a museum.

It's a cloud
where knowledge is traded.

[Narrator] The city only puts
one constraint on the design.

It mustn't block public access
to the end of point.

The land is so narrow,

this could seriously
restrict what they can build.

But Wolf has an idea.

[Wolf] The concept
of the building was

not only to organize
the exhibition spaces,

but to lift up the building
so that people can walk

to the point of confluence
and the park here.

[Narrator] The final design is a
gravity-defying building

that lays down the gauntlet
to the engineers.

How can we build it?

Because it was
like a flying building.

You have no idea how you can
work with the architect

just to understand
what is what is willing?

What is the objective
of the architect?

[Narrator]
It's clearly going to be

an enormous challenge
for the team.

First, they will need to
build a solid base

that's strong enough to support
the weight of the building,

while holding up
the huge columns

that will make it
appear to float.

Next, they will have to
construct a steel frame,

which will rest on top

and be covered
in 64,000 square feet

of stainless-steel sheets
to create Wolf's cloud.

Finally,
they will build the crystal.

A spectacular entrance
made from flowing glass panels

set into a thin steel frame.

At its heart will
be a whirlpool,

108 feet high,

and built of specially
curved glass.

It's known as the gravity well.

In 2010, construction begins.

And immediately the team
faces a major challenge.

They may have plans for an
extraordinary modern building,

but they're expected to build
it on land that literally sucks.

Building on reclaimed land
can potentially run

into all kinds of issues.

That area may be more
prone to flooding.

And because that land may
have once been a river,

it might be more unstable
and prone to subsidence.

[music]

[Narrator] Next,

even the architect
has second thoughts.

[Narrator] In 2010,
in Lyon, France,

work is underway to build
a magnificent new museum.

The only problem is,
it's on reclaimed land

made up of loose sand.

They said we should move it.

The government said, no, no way.

This is the most important
point in this city.

[Narrator]
So engineers design foundations,

which include 570 deep piles

with a reinforced concrete slab
sitting on top.

Onto that,

they plan to fix the columns
to hold up the massive cloud.

[Markus] We had to put a lot of
piles in to reinforce the earth.

We also lifted up,
even the plinth,

the concrete part
of this building

to be over the ground water.

[Narrator] It takes time
and an awful lot of concrete.

But there are now
solid foundations.

The next big challenge
is to work out how on earth

they're going to build the
enormous, show-stopping cloud.

To make it appear to float,

they take inspiration from an
old-world engineering idea.

Construction of the cloud
is the construction of a bridge.

[Ellie] A girder bridge is
perhaps the most classic bridge

design that you and I
are most familiar with.

The bridge deck is held up by
huge iron or concrete girders

that transfer the load
to the supporting columns.

[Narrator] At its heart, the
complex floating structure

is made up of a series of
interconnecting steel beams.

These allow the team to create
the unique cloud-like shape.

And just like a bridge,

the forces from this are
transferred to the ground

through a series of columns.

But its extraordinary
irregular shape

makes it difficult to calculate
how the loads will work.

A miscalculation could lead
to the engineering failing

and the building collapsing.

The cloud is very
hard to understand

and to describe
because it's a cloud.

So how do you describe the shape
of the cloud is not possible.

[Narrator] Hoping to make
the impossible, possible,

the team tries to
build a computer model,

but even that's not easy.

You let the computer
working one day,

you come back after one day,
you look at it,

and it doesn't function.

You have to try
another solution,

but you wait always one day

to have the response
of your idea.

[Narrator] Eventually, after
some serious number crunching,

the engineers arrive at a
structure that is as stable

as it is breathtaking.

The construction crew
gets to work building it.

Here you have really complex
connections of this different

secondary steel structures.

It worked well
due to this really

sophisticated 3D model.

[Narrator] Once the
main steel frame in place,

the team then creates
its irregular shape

by constructing
a smaller frame on top,

which is clad
in 64,000 square feet

of stainless-steel paneling.

The next challenge
facing the team

is how they're going
to build the crystal,

a massive glass atrium,
which will go at the front.

A challenge Wolf isn't
making any easier.

Basically, I hate columns.

To solve a stupid column

in many parts was the goal.

[Narrator] Wolf wants
to have an open space.

But it's vast and they need to
find a way to support the roof.

Because of this interaction
between all the elements,

it was very hard to achieve

the structural design
of the crystal.

[Narrator] The solution
for how to support the roof

lies in an extraordinary idea.

Imagination comes from,
from the turbulences

when two rivers coming together.

This is the experiment,
we did in our office

to see how a turbulence
look like when two streams

coming together.

Then this is the plan.

It's the columns
not being a column.

[Narrator] Wolf's idea
is to create a support

that doesn't look like a column.

So they make a void in
the middle of the atrium,

almost as if a giant finger
has pushed the roof down

to touch the floor.

Constructed from glass and steel
it looks perfectly in place

with the rest of the structure,

but it's also supporting
the entire roof.

The extraordinary mix of
sculpture and engineering

is nicknamed the gravity well.

If your structure contains
a cone-like shape that's

tapered to the ground,

the forces will be transferred
to the apex or tip of that cone.

So this shape is not only
interesting architecturally,

it also serves
a structural purpose.

[Narrator] The next challenge,

is making the structure strong
enough to be able to deal

with 15 feet of snow.

They start with a cladding

of specially
reinforced glass panels.

But the clever engineering
doesn't stop there.

[Marcus]
We have in the lower parts,

we have heated glass panels.

And the drainage is also heated

and the structure
is strong enough

to take the pressure of snow.

[Narrator] Finally in 2014,
after four years of construction

the Musée de Confluences
is complete,

and the results
are extraordinary.

It's a very open special,

not museum.

It's a building
for trading knowledge.

[Marcus] I'm very,
very, very proud.

And it was really great
to be part of this team.

[Gabriel] Maybe one time
in your life,

you make this kind of project.

So all your life,

you will remember and you
will remember this experience.

[Narrator] This cutting-edge
design transforms

what a museum can be,

creating an open, welcoming
space that beckons people in.

And just like the
two rivers that surround it,

it will bring people together
for years to come.