Original subtitles

[Jay Ellis] What happens when an architect

who's never designed a skyscraper

lets her imagination run wild?

[Sean Linnane] How the heck do you build 80-some floor plates,

no two of which are the same?

[Jay] How do you construct a 26-mile underground railroad

through the center of a bustling city?

[Chris Dulake] With all of these excavations underground,

it's a dangerous place to be.

[Jay] And how do you create a man-made wilderness

in the heart of an urban jungle?

The client was obsessed. "Make it as green as possible."

[Jay] This is the age of the extraordinary.

[Amma Agbedor] It's totally different

from anything around it.

It's like a visitor from another planet.

[Jay] Where ingenious engineers

have unleashed unchecked creativity.

Now their secrets are revealed

as we discover the amazing stories of their construction.

[Mat Picardal] You look at this building,

and your brain just screams at you,

"This building does not make sense!"

[Jay] To try and understand...

...how did they build that?

My favorite fact about skyscrapers

is that in strong winds,

they can sway by up to two feet in any direction.

Now, architects allow for this wherever they work,

but especially when the 82-story,

876-foot skyscraper they're building is in Chicago,

otherwise known as the Windy City.

So, when you see this next building,

all those wonderful shapes and sculpted ledges,

they aren't there just to look pretty.

[Jay] Chicago, Illinois, is the birthplace of the skyscraper.

And having built them for 140 years,

they've gotten pretty good at putting up your standard tower.

Thin, fat, short, tall, there's a lot of them here,

but most are hardly pushing at the boundaries.

[Jay] That is, until the start of the 21st century.

When the developer of a new high-rise

picked an unexpected architect for the job.

It was kind of a surprise, because I had never really

designed a tall building before.

[Jay] Her design for over 700 apartments and condos

with outdoor space challenged how skyscrapers look,

how they work, and how they're lived in.

This is Aqua Tower.

So, how did they build it?

It's 2006.

In downtown Chicago, near the shores of Lake Michigan,

a huge regeneration project is underway.

An area near the former docks,

once crisscrossed by railway tracks, is being transformed.

The next new building to go up will be a mixed-use skyscraper.

And it's going to be a big one.

The entitlements for the overall master plan

permitted a few of the building sites

to be extra large, extra tall.

Aqua was one of those.

[Jay] At over 800 feet, it will join an exclusive club

of the 20 tallest buildings in Chicago.

And the developer wanted to make an impact.

[Sean] It needed to stand out architecturally,

but it has to be financially viable.

And for a developer,

that often means kind of boring, rectangular buildings.

[Jay] To avoid that trap,

they turn to a local up-and-coming architect

whose work has been winning awards.

Her style is almost like an artist.

It's very sculptural.

[Jay] The choice comes with a huge risk.

[Amma] When you're building hundreds of feet into the sky,

you want a safe pair of hands,

meaning you want to work with a team

that's maybe done a project of this scale before.

[Jay] That most definitely isn't the case

with Jeanne Gang.

This was my first tall building.

I really didn't imagine that I would be

even doing a tall building at that point,

because most of my work was smaller scale

and with communities.

[Jay] That experience of working with communities, though,

inspires Gang to make this skyscraper different.

There wasn't much outside space for tall buildings,

especially in Chicago.

And there wasn't a way to easily meet your neighbors.

They were all kind of a bit isolating.

So it was really ripe for reinvention.

[Jay] Her design does just that.

It turned a blank, boring, rectangular building

into, really, a sculpture.

[Jay] What she comes up with is a blueprint

for an undulating building covered in rippling balconies.

Built in a densely developed area,

each is designed to maximize the views

and be perfectly placed for the residents to interact.

But making them a reality will be a huge engineering challenge.

First, they'll need to find a way to anchor

the 800-foot tall tower

in the notoriously unstable Chicago ground.

Then they'll have to design curved balconies

for the 82 floors, no two alike,

before building them to the demanding schedule

of a commercial development.

Finally, they must find a way to stop the wind

that typically whips around tall buildings

from making these precious outdoor spaces unusable.

In 2007, work starts on the foundations.

With the final tower measuring 876 feet tall,

they've got to be substantial.

The first step is to drill

massive steel and concrete foundation columns

100 feet down into the bedrock.

Usually, this would be fairly straightforward.

But here, there's a big problem.

Underneath this site is an abandoned railroad network.

The ground is riddled with disused tunnels.

It's like trying to drill piles into Swiss cheese.

If the foundations aren't rooted in solid ground,

it puts the whole building at risk.

[Jay] The team has no choice.

They're going to have to block off every tunnel

and then find a way to fill them

to make sure they don't collapse under the weight of the tower.

They decide the solution is something called flowable grout.

Flowable grout is an engineer's dream.

It'll fill the hole you need filled,

minimal shrinkage, it dries fast,

and you can pump it for long distances.

[Jay] They may know how to fix the problem,

but it's no easy job.

It's so dangerous working in those old, disused tunnels.

I mean, you have no idea what condition they're in.

Having a safe system to get the people down there,

putting in bulkheads to seal off the tunnels,

and eventually flooding them with the flowable grout.

So a lot of coordination and a lot of effort.

[Jay] It takes almost 5,500 cubic feet of grout

to fill the tunnels and three days for it to solidify.

Only then can the foundations be built and then capped off

with a 12-foot-thick steel reinforced concrete slab.

Next, the team turns its attention to the tower.

The key to its success is going to be the balconies.

As well as providing outdoor space

and a sense of connection to the neighbors,

Jeanne Gang hopes they will also give the residents good views.

Something unexpected in the boxed-in site.

The idea that I had was just to make it

almost like a topography that would allow you to, like,

kind of peek around the corner

where you normally wouldn't be able to see.

[Nehemiah Mabry] It's an incredibly simple

and clever idea to gain better views.

You essentially stretch the building out here and there.

[Jay] To work out the views from each balcony,

the team painstakingly uses a scale model of the area

and lots of string to show the sight lines.

Then they deploy computer modeling

to design each of the curving balconies,

which extend out between two to 12 feet.

Now, they have to work out how to build them.

To make the curved balconies look really elegant,

they need to be free from any visible support.

They need to look like they're holding up their own weight.

[Jay] To do that, they turn to a bit of engineering magic.

[Corina Kwami] The balconies are basically cantilevers,

so sticking out bits of the building that are made rigid,

and supported by hidden beams within the structure.

Our structural engineer gave us some parameters,

and so it was kind of like,

"Do it within these boundaries and draw within the lines."

We could cantilever more on the corners,

and less in certain areas.

[Jay] With the design down,

the next challenge is building the 82 floors

to the relentless demands of a commercial budget and schedule.

[Sean] For super tall buildings,

the faster you build the building,

the faster you can get to market and generate revenue.

So, a lot of the focus happens on

how long it actually takes to do an individual floor.

[Jay] The quickest and most efficient way

to pour floors is to have a repeatable design.

But to create Jeanne Gang's undulating balconies,

that won't work, because each is designed around the view.

You're looking at creating a unique and bespoke floor plate

for each and every floor.

How the heck do you build 80-some floor plates,

no two of which are the same?

[Jay] In Chicago,

the team building a new 867-foot-tall skyscraper

is wrestling with the challenge of building 82 floor plates,

no two the same.

It risks blowing a hole in the schedule and the budget.

So, the team comes up

with an ingenious, but experimental, system.

They create a giant tray.

Made in sections, it's big enough to hold

the entire floor plate of each story,

including the balconies.

Inside it, they carefully map out the curving balcony areas,

creating a special mold in steel.

[Randy Bullard] We started working with different gauges,

or thicknesses, of metal forming system

that would allow us to bend and curve

the form systems for each particular layout.

[Jay] The tray is then ready to fill with concrete.

[Dave Eckman] When the concrete had cured,

they were able to pull the flexible slab edge away,

which then just became a straight piece of steel again.

And then once that floor is done,

that steel can be moved

to do the same thing again with a different shape.

[Jay] It's not just the steel edging that gets reused.

With this system, the entire mold is, too.

[Eamonn] When the concrete had reached a sufficient strength,

the whole assembly would roll out like a kitchen drawer

and then be picked up by a tower crane,

and then flown up to the next level and repeated.

[Jay] With this kitchen drawer technique,

the building flies up.

[Sean] They got to a three-day pour cycle

for a floor plate that was somewhere between

14,000 and 15,000 square feet.

[Jay] As the tower rises,

the team has to take on its last big challenge:

the wind.

There's a reason why high-rise buildings

don't normally have balconies.

It can be incredibly windy up there.

[Jay] Not only can the wind

make the balconies uncomfortable to sit on,

it could make the entire building sway dramatically.

[Sean] High-rise buildings move.

It's a natural thing that they move.

They are designed to move.

You just don't want them moving too much.

[Jay] In a lot of tall buildings,

engineers put huge tanks of water or oil in the top floors,

which counteract the effect of the wind.

The problem is these take up so much space in the building

that could be used for the apartments.

[Jay] But at Aqua Tower,

the balconies are so cleverly designed,

there's no need for a counterweight at the top.

[Corina] By chopping up the surface of the building,

the balconies break up the wind,

dramatically reducing the impact on the tower.

[Jeanne] We've tested a model in the wind tunnel tests,

and yes, indeed, it actually does disrupt this wind flow

and helps with ameliorating the pressure on the building,

but also making it more comfortable.

[Jay] In 2009,

two years after breaking ground and three years sooner

than would be typical for a building this size,

Aqua Tower welcomes its first residents.

[Priscilla Mims] It is just exquisite.

There's really no other building in the city

that looks anything like it.

[Jay] It's a high-rise that offers its residents

an indoor-outdoor living experience like no other.

[John Fitterer] We live on the 68th floor.

I can go outside. I can get fresh air.

We have a summer party out there.

And it is very much like a community living at Aqua.

[Priscilla] It's a neighborhood within itself.

And it's amazing that just creating

that in-and-out pattern of the balconies

can do that to a tall building like this.

[Jay] In the birthplace of the skyscraper,

Aqua Tower has truly earned its place.

Aqua has really made its mark on the Chicago skyline.

Even if you don't live there,

you come upon it, and it's something special to discover.

[music]

For busy cities the world over,

good, fast, reliable public transportation is vital.

Over in London, a huge project to build a new subway line

beneath the streets of England's capital

was recently completed to great acclaim.

Although, the first train did arrive a little late.

A full 80 years, in fact,

after the project was first proposed.

But, boy, was it worth the wait.

[Jay] Welcome to the Elizabeth Line.

A 73-mile-long railroad

complete with 10 brand-new state-of-the-art stations.

To build it, the team had to dig 26 miles worth

of underground tunnels.

The scale of the engineering is breathtaking.

[Jay] The challenges and risks

were like nothing encountered before.

We're tunneling under the most expensive property in Europe.

[Jay] At stake was a city-wide subway

designed to last 120 years.

[Howard Smith] The Elizabeth Line is

a once-in-a-generation railway,

a legacy that will just grow and grow over the decades to come.

[Jay] The result provides passengers

with a smooth, spacious, and very speedy journey

across the capital of the United Kingdom.

The Elizabeth Line is one of the 21st century's

greatest infrastructure projects.

[Jay] So how did they build it?

[Jay] Britain is the birthplace of the railroad.

But the way the system evolved in its early days

left the capital, London, with an enduring problem.

In the 1840s, so many people wanted to build railways

in London, that there were plans to cover

almost the whole of Central London in railways.

So a royal commission said,

"Let's keep railways to the edge of the city."

[Jay] With all the trains ending at the outskirts of the city,

passengers were forced to take

alternative transportation into the center.

Even when the subway arrived a few decades later,

it didn't resolve the issue.

Everybody was getting off big trains, going down escalators,

and getting onto small trains

to go around the center of the city.

[Jay] In the 1940s, when the city was looking to rebuild

after World War II,

a plan was devised for a new cross-London railroad.

It would take passengers through the heart of the city

on underground tracks without changing trains.

But with so many other infrastructure projects

needed in the aftermath of the war, it took a back seat.

Fast forward six decades,

and a new version of the idea is on the table.

[Howard] From 2004 onwards,

we got to planning what's become the Elizabeth Line.

So, it's an old idea of taking big trains

and allowing people to travel straight through,

from outside into the middle of town,

and one that's become a reality for London in the last 20 years.

[Jay] The daring plan is to carve out

a 73-mile continuous route

that will start 40 miles west of the city,

passing through Heathrow Airport,

through the city center,

and then to the UK's financial center at Canary Wharf,

before terminating 20 miles further east.

The main challenge will involve sinking a 26-mile network

of supersized tunnels deep beneath the city.

Eight giant tunneling machines

will have to excavate interconnecting routes,

starting from the west and the east of London,

before meeting in the middle.

The team will also have to design

ten giant new stations

that will serve both the new and existing subway lines,

Integrating the Elizabeth Line

with the existing transportation network.

In May 2009, work starts on the first of ten new stations.

Canary Wharf in East London,

where a huge $650 million US underground station

must be built in time for the eastern tunnel

to pass through it,

before meeting the western tunnel in Central London.

[David Johnson] The real challenge for Canary Wharf

was if there were any problems with the construction works,

we would then delay all of the tunneling works,

and that would have a knock

on to the whole completion of the project.

[Jay] The challenge for engineers

is that Canary Wharf sits on the River Thames,

and the proposed station will be

in one of London's historic docks, 90 feet underwater.

[David] All of the works were within the water

of the West India docks.

This gave us a lot of challenges in terms of

how we could dewater the docks to construct the station.

[Jay] To create a dry construction site

in the middle of a dock calls for

a clever piece of engineering known as a cofferdam.

Similar to the lock on a canal,

it works by damming water on one side

so the other side can be drained dry.

It's tricky enough to achieve on any site,

but here the challenge is even greater.

[David] The traditional cofferdam construction

would use sheet piles,

which would either be vibrated or driven into the ground.

This would obviously create lots of noise

and lots of vibration from the works.

[Jay] But Canary Wharf is home to the UK's financial district,

and the headquarters

of some of the world's largest banks, and insurers.

We had 100,000 people working around the site,

and also hotels and residents in close proximity,

and we couldn't spend three or four months hammering

or vibrating sheet piles into the ground.

[Jay] They need to find a way

to build the cofferdam silently.

[David] We actually had two machines

specifically made for the project

that were shipped over from Japan,

where they'd already developed a system

for pressing in large diameter tubes

into similar ground conditions.

[Jay] It's the first time this type of engineering

has been used in the UK.

Instead of hammering,

the Japanese method silently presses and pulls

the sheet piles into place, using hydraulics.

One by one, the interlocking sheet piles,

each 61 feet high and 4 feet wide,

are pressed into the dock bed.

[David] We targeted to install three piles per day,

and we did that over three months,

and completed 310 piles,

installed within about a four month period.

[Jay] The last step is to pump the cofferdam dry.

Over three weeks, we pumped out 60 Olympic-sized swimming pools

in terms of volume of water from the cofferdam

to create our dry working site.

[Jay] Now, the giant new underground station

can begin to take shape.

[Howard] A great big concrete box

constructed 260 meters long.

You could tip some of the really big buildings in London,

put them on their side, and they'd fit quite neatly

into something like Canary Wharf Station.

[Jay] With the station work progressing,

the team can move on to their next challenge,

and it's a big one.

[Jay] To create the 26-mile underground section

of the route, they need to start digging.

[Corina] The machines you need for a job like this

are not available at Home Depot.

And there are only a handful of companies that actually

manufacture the equipment that is required to do this job.

[Jay] The equipment in question is a tunnel boring machine,

or TBM, worth $15 million US apiece.

The team orders eight from Germany,

but they're too big to ship whole,

so they're delivered in pieces and rebuilt on site.

It's no easy task.

[Corina] Building a TBM is like building a bridge,

or a major piece of infrastructure.

You have to build foundations where you're making the TBM.

It's that heavy.

[Jay] Finally, in May 2012, tunneling begins.

[Chris Dulake] It was phenomenal.

It was an exciting time for anybody involved.

[Jay] They operate like huge mechanical worms,

chewing at the face of the tunnel,

and pulling earth onto an internal screw conveyor.

That earth is then expelled from the rear of the machine.

Designed to work 24-7,

they can bore 330 feet of tunnel per week,

operated by a crew of 12 inside.

If everything goes to plan.

But that's a big if when you're tunneling under the center

of one of Europe's biggest cities.

The industry has a bad track record

in collapses in urban centers.

[Mat Picardal] The greatest risk you face when

you're digging underground is support.

How do you make sure the earth around you holds up

when you're burrowing down?

[Jay] If the tunnels collapse underground,

then the buildings above could sink.

The team needs to tread extremely carefully.

[Chris] With all of these excavations underground,

as soon as you lose control, it's a dangerous place to be.

[music]

[Jay] In London, engineers building a new rail line

with ten new stations and 26 miles of track

running deep beneath the city

need to make sure their enormous tunnel boring machines

won't destabilize buildings above as they dig.

Part of the solution comes from

the machine's ingenious in-built technology.

[Chris] As they drive forward,

you're able build a precast concrete lining

behind the machine from a series of rams

that sit around the outside of the machine

that enable you to lock that lining in

and then drive forward.

[Jay] Shoring up the tunnel as they go isn't enough.

The drivers also need to maintain

steady and constant pressure at the machine's cutting edge.

If we didn't control that amount of movement

and that face pressure,

we could induce quite a bit of ground movement

that would have affected the buildings above us.

[Jay] The slightest movement underground

can have huge consequences above.

[Jay] As the Western Tunnel reaches

London's theater and shopping district,

engineers monitor the impact of micro-movements

on some of Europe's most expensive real estate.

[Chris] And there were some significant buildings

that we were tunneling under.

So for every single structure that fell within

the one-millimeter contour of movement at surface,

we predicted the level of damage

to the building that would occur,

and if it was an unacceptable level of damage,

we applied a process called compensation grouting.

[Jay] It works by injecting high-pressure grout

underneath the building, which expands, lifting it up.

[Chris] It sounds like a complex process,

but as the buildings above settle,

as you tunnel underneath, you compensate for that movement

by pushing them back up.

We installed about 60 kilometers

of pipework to deal with those movements.

And yeah, they worked very well.

[Jay] While the network of tunnels takes shape,

teams are hard at work across London

completing the ten new stations.

It means even more digging,

and creates one heck of a pile of dirt.

[Chris] All of those underground constructions in London

totaled about 6 million cubic meters of material.

And so the biggest challenge was getting that out of London

without impacting on the public.

[Jay] Removing it by truck will add

half a million road journeys

to an already congested capital.

For moving that sort of stuff any distance,

you want to put it on rail or you want to put it on water.

[Jay] The answer runs through the heart of London,

the River Thames.

[Howard] Night and day, conveyors running,

bringing spoil out into barges and taken down the Thames.

[Jay] Even better, all that earth doesn't go to waste.

25 miles along the estuary, it's used to create

an entirely new wetland and bird sanctuary.

We had over 4 million meters cubed of material placed there.

And that enabled us to then break the seawalls down,

so that we allowed the tide to come back in over those areas,

then reinstated a wetland.

[Jay] In 2022, the Elizabeth Line opens.

With over 130 million journeys made on it each year,

it has expanded London's rail capacity by 10%.

[Julian Robinson] To leave a great piece

of infrastructure for London, fantastic.

What do you ask for in a career?

[Jay] In the ten new stations,

smooth, sculpted concrete tunnels

encourage people to flow through them,

While clever lighting maximizes the sense of space.

Every detail has been thought through,

right down to how they sound.

[Neil McClements] We incorporated thousands

of acoustic perforations into the crown of the tunnels.

And this creates a really soft acoustic environment

for passengers, a calm, almost Zen-like atmosphere

away from the hustle and bustle of the city above.

[Jay] The line is predicted to add $55 billion

to the British economy.

And it's connected dozens

of previously underserved communities.

People are able to look for new houses or for new jobs

that they couldn't have got to before.

You know, that's a boost to the city itself.

The Elizabeth Line?

Game changer. Absolute game changer.

[music]

Azabudai Hills might not sound like

a bustling neighborhood development

in the center of the Japanese capital of Tokyo,

but this earthquake-proof wonder is way more green

than its urban location might suggest.

Not only does this city within a city

have a living roof from which thousands of plants

grow down to ground level,

it also processes sewage, and then uses it

to control the indoor climate. Genius.

At 37 million people,

Tokyo has the highest population of any city in the world.

And they all need somewhere to live and work.

Tokyo has one of the lowest areas of natural greenery

per person for a large city in the world.

[Jay] But in the late 1980s,

a developer set out to change that

with a groundbreaking piece of urban planning.

Creating a complex of homes, offices,

a hotel, shops, and restaurant,

including the tallest skyscraper Japan has ever seen.

[speaking Japanese]

[Jay] And surrounded by six acres of green space

in the heart of the city.

The client was obsessed, "Make it as green as possible."

[Jay] Realizing this vision took almost 35 years.

It meant negotiating with over 300 landowners.

The team had to ensure it would survive in one of the most

earthquake-prone cities in the world.

Building in a zone like this is, everything has to be bigger.

Everything is much more tightly braced.

[Jay] All in a bid to change the face of Tokyo forever.

This is Azabudai Hills.

So, how did they build it?

Half of Tokyo was destroyed by Allied bombing

in the Second World War.

In the postwar years, the city saw a huge redevelopment,

but money was concentrated on buildings, not green spaces.

Toward the end of the millennium,

people were realizing how detrimental this could be.

[Corina] Studies have shown that green areas in cities

not only mitigate climate change and improve air quality,

but also bring communities together

and contribute to the local economy.

[Jay] In the late 1980s, developers Mori Building

decided to transform a 20-acre area of downtown Tokyo.

Their vision is to create a green oasis

where people can live, work, and play.

[speaking Japanese]

[Jay] To do this, they will first need to get

more than 300 individual property owners

to agree to their land being redeveloped.

Then, the plan is to put

most of the living, working, and retail space into three towers,

one of which will be Japan's tallest building,

leaving room to create six acres of green space

across the complex.

We're building seven or eight million square feet,

but it's all vertical.

It preserves the land for human use, for green space.

It's a much, much better way to build a city.

[Jay] The team knows this will be a model

for other cities to follow.

So, it will need a revolutionary design.

To start, they will need to demolish

the existing buildings on the site.

Then, create separate foundations

for the three towers,

individually suited to their different needs.

After that, they will need to figure out how to

make sure the tallest building in Japan will stand strong

in the most earthquake-prone city in the world.

Finally, they'll have to fit in shops, bars, and restaurants

at ground level, while also creating the lush green spaces

that the client wants.

The piece of land chosen for the project

is in the densely populated Minato area of Tokyo.

The first challenge is persuading

more than 300 individual landowners

to agree to the redevelopment.

It's like taking on a project

the scale of the Rockefeller Center in Manhattan,

and getting 300 individuals to cooperate in making it happen.

[Jay] No easy task.

But in exchange, they are offered units

in the completed development.

[speaking Japanese]

[Jay] Not surprisingly, it's a slow process.

In Japanese culture, building consensus is really important.

They even have a special word for it called nemawashi.

And things take as long as they need to.

[Jay] No one could have predicted, though,

that it would take more than three decades.

[music]

[Jay] In Tokyo, Japan,

it's taken over 30 years to win over more than 300 landowners

and navigate the complex Japanese planning system.

But finally, in 2019,

work begins on a bold new mixed-use development,

incorporating not one, but three skyscrapers

surrounded by acres of greenery.

Building this anywhere would be a challenge.

But here, it's especially difficult.

Tokyo is a hugely active earthquake zone.

So, authorities prefer to keep buildings

shorter and wider to make them earthquake resistant.

Here though, architects Nihon Seiki

and U.S. firm Pelli Clark & Partners

must work together to design three huge towers,

including the tallest Japan has ever seen.

Earthquake-proofing them starts from the foundations.

All of the towers are sitting on

what is called a matte foundation.

It's a very stable, huge slab of concrete, frankly,

embedded in the earth.

It is critical in the sense that it spreads

the weight of the building over this big concrete platform.

It doesn't concentrate the weight in any singular are.

[Jay] The tallest tower will be 1,000 feet.

Building its 16-foot-thick matte foundations

takes 15 months.

By 2020, after a total of 274,000 cubic yards

of concrete have been poured,

the groundworks for the entire complex are complete.

The next challenge is to design and build

the steel structure for the towers.

These also must be super strong.

[Michael Lewis] The main thing is structure is big.

The columns are much bigger than we're used to.

The beams are much bigger than we're used to.

And, of course, you have to brace a lot more.

[Jay] In an earthquake zone, strength needs to be balanced

with flexibility so that the building can move

and absorb the impact

without collapsing under the strain.

And because the effects of an earthquake on a skyscraper

are magnified the taller it is,

the team has to use every shake-resisting trick

in the book.

The towers will be fitted with giant oil dampers,

or shock absorbers,

more than 300 in the tallest tower alone.

But the seismic measures don't stop there.

[speaking Japanese]

[Jay] They design 1,200 metal braces

in the walls.

Made from soft steel, they effectively absorb energy

during large quakes.

And they'll add huge weights at the top of each tower.

These will move in the opposite direction

to the building during an earthquake

to counteract the swaying motion.

For most buildings, they only usually have one or two

of these technologies, but this building has all of them.

[Jay] With the tower safe,

the team moves on to making them green,

including installing a very unusual heat recovery system.

[speaking Japanese]

[Jay] Using the sewage to heat the building in the winter

will reduce the tower's CO2 emissions

by about 70 tons a year.

As the towers near completion,

the team faces a fresh challenge.

Realizing the vision for a natural green wilderness

in the heart of the city.

Although the skyscrapers

have freed up space at ground level,

this premium city real estate

is also needed for shops and restaurants.

Figuring out how to squeeze in enough greenery

falls to Heatherwick Studio.

The green area requirements for this area

in Tokyo are quite ambitious.

It was clear that we wouldn't just be able to have

conventional buildings next to a garden,

that we would need to integrate the two.

[Jay] Luckily, Heatherwick's previous projects include

1,000 Trees in Shanghai and Little Island in New York.

So they know about imaginative ways to green a city.

We almost started with a diagram of

"What if it's just a green valley?

And in fact, our site sat within a natural valley?"

And we started to think, "Well,

"could we just exaggerate the valley in some way?

Could we start to lift up this landscape?"

[Jay] They devise a world first.

A giant pergola will stretch like a net over the shops below

and be covered in plants.

The big question is how to build it.

The construction of the pergola system has been

probably the biggest challenge on this project for us.

The geometry itself is obviously curved.

It's curved in elevations, but it's also curved in profile.

Which means that you don't just have a single curve,

you have what we call a double curve.

[Jay] To create the undulating double curves,

Heatherwick works with the architects and engineers

to design a custom frame built from bent pieces of steel.

Before a more natural-looking finish, they want to

cover it in panels of glass fiber reinforced concrete.

This is a very lightweight concrete,

which means you can get very thin panels

and use a lot less concrete.

It also is reinforced with glass fiber,

not steel, which makes it lighter and easier to make.

[Jay] These specialist panels will be prefabricated offsite.

and craned into position.

The problem is they need so much of this special material

that Japan runs out.

Production switches to China, which means shipping them over.

[Michael] Shipping panels from one country to another,

it's not just as easy as finding a ship to do it.

You have to look at controlling the temperature

of the concrete panels,

controlling the moisture content of the shipment vessel,

because any change in the moisture content, or too much

of a change in temperature could compromise the panel.

[Jay] After a nervous wait,

in 2020, the panels arrive unscathed.

Now comes the task of assembling the intricate,

curving, three-dimensional jigsaw puzzle.

Our biggest fear was the coordination of those

concrete panels with the other components on the facades.

[Jay] If this complex puzzle doesn't go as planned,

the pergola is at risk of collapse.

[Michael] So you have concrete meeting aluminum curtain walls

or concrete meeting the floor where it meets stone paving.

[Jay] To make matters worse,

it's the middle of the COVID-19 pandemic,

and the architects are stuck in London,

unable to supervise in person.

We've had some long calls. Six or seven hour calls.

It was very stressful, that time.

[Jay] Over the coming months,

the team follows things remotely,

and watches as everything falls into place.

All that's left is to fill the pergolas with the 320 varieties

of plants and trees that will breathe new life

into this corner of Tokyo.

In November 2023,

after nearly 35 years of waiting,

Azabudai Hills finally welcomes back residents.

And it's a triumph on a huge scale.

It's really unusual to feel such a natural and wild environment

in the center of a city,

and I think that's been the biggest surprise for me.

[Jay] Over 90% of the previous occupants

have opted to return here to live.

[speaking Japanese]

[Jay] They've done the seemingly impossible,

creating a lush green space in the middle of Tokyo,

and building the tallest tower in Japan

capable of withstanding the most violent earthquake.

There's individual elements that I love and little moments

where I like to kind of go and spot and walk through.

I guess the one thing I'm really proud is

how it all stitches together.

[Jay] They have created a model for urban living

that could inspire a generation.

For me, Azabudai Hills is the pinnacle of my career.

[music]

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