Original subtitles

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narrator: Like no other,

this enormous, state-of-the-art building

dominates the entire city that surrounds it.

Andrew steele: The singapore national stadium

is a truly epic structure.

Benjamin flowers: It's simply undeniably unique.

Roma agrawal: You have this beacon of light

coming off the top of it.

Narrator: The multi-award-winning sports arena

is a dazzling symbol of singapore's national pride,

but more than that,

it's architecture on a scale never previously achieved.

Steele: It's the largest free-spanning dome in the world.

Narrator: How on earth do you build a dome this big?

Agrawal: It's, you know, a real marvel

of structural engineering.

Narrator: When it opened in June 2014,

the spectacular ceremony marked the end of a torturous battle

against the laws of nature.

Physics as well as the climate,

and even the land the stadium is built on,

presented a deluge of horrendous hurdles

that came close to defeating designers.

Clive lewis: Obviously it's a major project

with huge challenges along the way

to making it and realizing it.

Narrator: The only way to find out

how architects and engineers won the battle

to turn the stadium into a successful reality

is to take it apart and reveal the innovations

hidden within it.

The futuristic singapore national stadium

is the centerpiece of a giant $1.3 billion sports hub.

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dreamed up at the start of the millennium,

the intention was to give the city-state

a glossy, new, forward-looking image

with a stadium that could host

prestigious international events.

Oon jin teik: Back in 2000, the year 2000,

singapore was really looking at transforming itself.

It is a red dot, little red dot

in the context of neighboring countries

in this part of the world.

We may be small, but the dreams and aspirations of singapore

is actually very bold, very big.

Narrator: Today the stadium stands as a testament

to those grand aspirations.

Lewis: The national stadium is the largest free-spanning dome

in the world, spanning over 1,000 feet.

The range of engineering disciplines

that we were controlling was beyond anything

I've done before in my career.

Narrator: Designing a venue that delivers

a great experience to tens of thousands of people all at once

is quite different to any other engineering challenge.

And for architects, a stadium can be

the most creative project of all.

Flowers: This is incredibly hard to do,

it requires a vast investment in technology to engineer that.

And so you have to have the right kind

of geological conditions

and the right kind of infrastructure systems in place

to support the building both during its construction

and during its lifetime.

Mike king: All of these buildings are one-offs, you know.

You're not doing it as number seven in a series of ten,

you know, these are each unique buildings

with their own constraints and their own set of reasons

for coming up with various aspects of the designs.

Narrator: The problems to overcome can be anything

from crowd transportation

to the sourcing of building materials.

For the singapore national stadium,

there is one issue that will never go away.

(thunder)

jin teik: We are located in a tropical zone

where it not just rain, it pours cats and dogs, right?

Narrator: In the 1970s, the first national stadium

was built on the same site.

But it was open-air and completely useless

against the elements.

Right from the start, the brief for the new stadium

insisted on a weatherproof roof.

The architects could only come up with one solution.

It was radical and would be a huge and very public gamble,

because it had never been attempted

on this scale until now.

King: There's a huge amount of pressure,

and you're always feeling that if it didn't work this time,

then you didn't have an alternative.

Flowers: To build an actual structurally sound, solid roof

over a stadium is a feat of engineering of some distinction.

Narrator: For starters, the area of a stadium roof is vast.

And that means weight, lots of it.

Several stadium roofs have collapsed.

Flowers: You have to think about the obstacles you face

whenever you enclose a stadium of any kind,

which is how do you hold the roof up?

And in most conventional stadiums

that was done with columns.

Narrator: Columns are very effective

for supporting flat roofs.

But any column system inside a stadium

has a fundamental disadvantage.

Maxwell hutchinson: In a large sporting arena,

the starting point for the designer

is the field of view of the spectator.

They want to be able to see what's going on.

(cheering)

flowers: You don't want a column interfering with the view

of the fans sitting behind it of the action on the pitch.

So how do you deal with that?

Narrator: For the new singapore national stadium,

any design with columns is ruled out.

But a roof is still a requirement,

and it must be supported somehow.

Architects delve into history for inspiration.

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king: Going back to sort of roman bridges and the like,

the arch has always been a very natural form

for resisting uniform gravity loads.

That's why they work well for bridges, and even naturally,

you know, the natural arches that would form in rock.

Agrawal: If you think about the arch,

you've got this curved structure,

and when you put a uniform weight on top of that arch,

the arch basically channels all of that load

into the bottom of the arch,

but it keeps the entire structure in compression.

So what that means is it's being squashed together.

Hutchinson: You take an arch and just keep on rotating it

and rotating it and rotating it, you get a dome.

King: Not only is that efficient for resisting

a uniform downward load, because it's a three-dimensional system,

it actually has quite a lot of resistance

to buckling out of shape.

Narrator: The architects choose a dome for the roof,

but they go a step further and plan the entire structure

to be contained in the dome.

Flowers: As is the case with anything, with any building,

scale matters.

So sometimes when you do something that we know well,

but you just do it a lot larger, the impact really is tremendous.

Narrator: But what about the weight problem

that a roof of this scale inevitably poses?

The stadium's first secret lies underneath its outer shell.

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there are no supporting walls.

The whole building is basically a roof, a lightweight dome

formed by a number of gigantic metal arches.

Six steel trusses span from side to side,

and at 90 degrees to them there are giant transverse trusses.

Together they hold up the whole roof.

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agrawal: Trusses with lattice structures

are structural engineers' favorites,

because they've got triangles in them,

and triangles are really, really stable shapes,

they don't deform.

So if you imagine that you had a rectangle shape

and if you put kind of funny forces onto it,

it can deform into a diamond,

but triangles just don't do that.

Narrator: There are over 11,000 tons of steel

in this monumental structure.

But in 2008, when the design team

are still drawing up plans,

the global financial crash takes its toll

and steel prices rise, all too aptly, right through the roof.

King: When we initially did the design of this,

we had almost double the amount of steel that was in the roof,

and then as steel prices escalated,

then there was a real drive

to say, okay, how can we drive efficiency into this?

Narrator: To stop the project going way over budget,

the team urgently needs a revised design.

Lewis: Our design mantra was to reduce weight everywhere

in the structure of that dome,

so we got the best, most efficient shell structure.

Everything had to be optimized to a minimum weight

to make that a very efficient dome.

Narrator: They create an innovative computer program

that can work out the minimum amount of steel

that would still meet the structural requirement.

Lewis: We developed a very bespoke piece of software

to achieve optimization of every element

within that roof structure,

whether that was the thickness of the steel

or the diameter of the tube, it was all optimized

to make it the lightest steel structure possible.

King: 20, 30 years ago, you just couldn't do that.

It would take you years to do the sort of design

that we've done here in a matter of months.

Narrator: The result is a world record-breaking dome

that is so large,

the sydney opera house would fit inside it.

King: All of the sections are hollow,

so they're all hollow tubular sections,

so you make them as thin and as light as you can.

You're up here and you're looking at it in various angles,

and everything just looks right and it looks in balance,

because everything is here for a reason.

Narrator: Reducing the amount of steel

cleverly saved the budget going bust

before construction had even started.

King: If you took all of the steel in the roof

and you melted it down

and laid it down on the footprint of the building,

you'd only have 15 millimeters of steel.

Agrawal: The structure that makes it up

looks really light and elegant and slender,

so I think it's, you know,

a real marvel of structural engineering.

Narrator: One challenge down.

But the roof design is just the start.

Making it hold its own weight is one thing,

firmly attaching it to the ground is quite another.

Narrator: When the high-tech singapore national stadium

was built, the construction team faced a serious problem.

The local terrain was completely unsuitable

for erecting a large, heavy building.

King: Because it's reclaimed land,

directly underneath the grass and the topsoil here,

we have a lot of what's called marine clay,

and marine clay is about as useful as dark gray toothpaste

to build a building on.

It really is just muck.

If you were coming down onto rock,

the force from the dome could go directly into the rock.

We don't have that advantage here.

Narrator: The poor ground threatened the whole project,

but there was a clever solution right in front of them.

King: We started with the demolition of the old stadium

here in late 2010.

The old stadium was crushed up.

Lewis: All of the concrete was used as either a base

or some parts of the ground forming for landscape.

Narrator: And on top of that debris,

a rock solid base of concrete.

Hutchinson: The singapore stadium is built off

what is called a raft foundation.

Now, that is a large concrete slab over the ground.

Narrator: Unfortunately, the raft foundation alone

is not enough.

The dome's weight pushes out as well as down.

It would collapse into a giant pancake

unless something holds it in.

Once again, the engineers look

to historic masters for inspiration.

Hutchinson: In the historic domes, like florence cathedral

or st. Paul's, is a chain, a metal chain.

So you put a metal chain around the edges,

so where all the weight of the dome comes down

and is trying to pull out, it's restrained.

Narrator: Engineers stole that renaissance concept

and came up with what's known as a ring beam.

Instead of using a chain above ground,

they buried it in the foundations.

Hutchinson: In the singapore stadium,

the dome is restrained at the edge by steelwork

that it must be completely continuous,

as if it were a chain, to stop the dome pushing out.

It relies upon being one structure

with complete, undamaged integrity.

King: So what I'm standing on the edge of at the moment

is the ring beam, and it contains 14 ducts

of very high-strength steel cables,

and those cables, the amount of force that we put in those,

we've pre-stressed them, is around 4,000 tons.

So it's a huge amount of force.

The ring beam is like a large, very strong, elastic band

that's pulling it back in

so that all those legs don't spread.

Narrator: Most critical is where the huge trusses

meet the ring beam.

A single error here, and the trusses would explode out.

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king: So these are some of the most complex and nerve-racking

parts of the project to construct,

and we call them the thrust blocks.

So the entire roof, which is 9,000 tons of steel

and around 15,000 tons total weight,

comes down on only 20 of these supports.

So you can imagine how hard they're working.

Narrator: The weight of the whole structure

is directed down onto these huge thrust blocks.

The only way to understand

how they're locked onto the ring beam

is to look inside one of them.

Hidden within the giant concrete block is the secret.

175 metal rods called shear keys

penetrate right into the heart of the ring beam.

Their length and diameter perfectly calculated

to be just enough to completely secure the truss.

King: Bringing this down, just to get 175 shear keys

to sit inside that reinforced mat,

was one of the most challenging elements of the whole job.

Narrator: The next aspect of the project

is where the real headaches start.

The pitch is made of live grass,

which leads to another complex engineering problem.

The enormous roof has to open and close.

Lewis: The moving roof did pose challenges for us, you know,

quite commonly they're done on a flatter roof profile,

and they're very linear in their opening and closing arrangement.

Doing it on a sphere created some real challenges for us.

Narrator: The moveable sections each cover 100,000 square feet,

and because they're curved,

getting them to move at all is a mechanic's nightmare.

King: The retractable roof is around 1,000 ton per leaf.

There's two leaves that open and close.

So the roof had to be very strong and very stable.

Narrator: The design was for the moveable leaves

to run on rails, but there was a dilemma.

Any expansion or contraction of the metal components

could make the panels jam.

So they couldn't be too rigid.

King: We worked out very early

that we should have a very stiff, fixed roof,

but then kind of a floppy, retractable roof

that could kind of bend and move a little bit.

Steele: The solution that engineers ended up using

was an incredibly efficient winch system,

with winches mounted on that retractable roof

to reduce the amount of cable that was required.

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aaron wong: When you are wheeling in,

it pulls the roof upwards to close.

When we are lowering the roof, the majority of the lowering,

the work is done by sheer gravity.

Narrator: The roof panels are mounted on rails

attached to the arched trusses.

Powerful winches on the base of each panel heave them up

to close the roof,

and the cables take the strain when it opens.

But here's where it's really smart.

Sensors monitor exactly where the panels are,

preventing them from ever skewing

more than an inch and a half.

And to reduce friction,

the number of wheels in the system is kept to a minimum.

King: If we reduce the number of points

that it actually hangs from, or the driving points,

then that will also reduce the possibility

of the whole thing jamming.

Wong: This silver-looking strip is like a barcode,

and the position sensor actually reads off this silver strip

to inform back to the event control room

where the control system is,

on the position of the roof at any one point of time.

So this is tracked very closely.

And one fun fact is that it's so sensitive

that even a drop of water

would actually cause the entire system to stop.

Narrator: The retractable roof is a key feature

of the stadium.

Incredibly, it can open or close in just 20 minutes.

Thanks largely to lightweight inflatable pillows

of plastic called etfe, which make up its skin.

Sean de rozario: Basically, all aspects of the roof movement

is actually controlled here from the event control room.

We've already done our last checks,

mission control is good to go, and we hit the button.

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wong: Operating such a huge structure,

it's better to have as little heavy elements

as possible as we can.

One primary reason why it needs to be inflated

is to allow water to run off, so that it is not a flat surface.

If it's flat, water can collect,

or if it's sagging, water can collect.

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narrator: Today the maintenance team are out, using a drone.

Wong: We're actually flying above and outside of the stadium

because we actually get to go to places

where even the remote access technicians

would have great difficulty getting to.

So over there we are actually able to scan

the entire outer shell, outer dome of the stadium itself.

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king: If you're in the tropics or you're equatorial,

like we are here in singapore, and you're coastal,

then you have salt in the air,

you have a hot, humid environment,

things rust very, very quickly.

De rozario: So with the drone we are actually able

to go up there, start to inspect for things, see whether there,

let's say for example, are there any abnormal rust streaks

coming down from the roof?

Are there any panels that look misaligned?

Is there anything that really looks off?

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on occasion when the pitch is in,

we actually use it to monitor the quality of the pitch

and to actually see how well the grass is growing

on a frequent basis.

Narrator: Keeping a vigilant eye on the state of the turf

is vital for any venue that holds world class soccer,

rugby or cricket events.

But for the singapore stadium, it's now especially important,

because soon after the pitch was planted,

there was a disaster.

Steele: Unfortunately there just wasn't enough light

getting into the stadium, and the grass, it died.

Narrator: The singapore national stadium

is one of the most high-tech sporting arenas in the world.

But when it opened, it had serious teething problems

with one vital component:

The turf.

Jonathan teo: In any sports stadium,

the pitch would be the crown jewel,

because this is where all the football action, rugby action,

all those events or activities happen here,

and you have a full house of 50,000 people watching.

So I would say the pitch would be most important.

Steele: One of the huge challenges building a stadium

like this is that you've got a living thing at its center,

this huge lawn that's got to be kept

in absolutely tiptop condition

for international sporting events.

Jin teik: Because we are located in a tropical zone,

because we have a retractable roof,

it is not so simple to just grow grass in this climate.

Teo: So the five key elements of growing grass:

You need light, water, temperature, air,

and of course nutrients.

So, to keep this grass healthy,

these five elements are important.

In a dome where we have shade and all that,

first of all, the light is compromised.

Steele: When the stadium opened, disaster struck.

At the center, the crowning glory of this stadium

is its beautiful, flat,

international quality grass pitch.

But unfortunately there just wasn't enough light

getting into the stadium, and the grass, it died.

Narrator: More than an embarrassment,

the withered grass threatens

the fundamental viability of the stadium.

Detractors called it a white elephant,

a colossal waste of money.

Footballers like carlos tevez are prevented from playing

on the substandard turf.

Steele: When it got to the point that managers weren't allowing

their star players onto the pitch

for fear that the terrible, sandy condition of it

would cause them injuries, something had to be done.

Jin teik: In initial days we used the stadium growth lights

to enhance the exposure of light.

Steele: This problem with the grass was so fundamental

that they tried everything to solve it,

and they spent a phenomenal amount of money

trying to just blast this grass with artificial light

to help it grow.

Narrator: But the light isn't the problem.

The grass still stubbornly refuses to grow properly.

Desperate for a solution, they take a major gamble

and commission a brand new type of turf.

Teo: We are now currently at the nursery

where I grow all my grass, my pitches.

This is where I do all the work, the start of the journey,

before all the grass rolls get all rolled up

and go into the national stadium for events.

Narrator: At an offsite location

away from the stadium,

jonathan and his team of horticulturalists

experiment with different types of grass.

Teo: To some point, my family actually finds it quite queer

and sometimes funny, what I do.

I get out very early in the morning

and I come back when the sun is setting,

and they do wonder what I do.

Until I take them to the park and I explain to them

the different grass types and how is it maintained,

and they go, wow!

We are doing a traction test here,

and this is a portable traction tool,

and as it rotates, you have a reading on the wrench here,

and the time when we stop

is when we hear the grass almost tearing,

and we look at the reading from here.

So a good traction would be about 40.

So this is what we're trying to achieve

to get it ready for the national stadium.

Narrator: Eventually they choose a brand-new hybrid turf

that is part real grass and part synthetic fiber.

Teo: This is the section of the turf rolls of the hybrid system.

It's reinforced turf, as you can see,

there's some fibers that's intertwined with the turf grass.

Of course, the grass matters a lot as well.

It's just a combination of both, that's why it's a hybrid.

Narrator: The big advantage of the nursery

is that spare pitches can be grown here

and transported to the stadium whenever they're needed.

The hybrid turf has 7% synthetic fibers

mixed in with live grass

to give the cutting-edge playing surface consistence.

A layer of high-grade sand aids traction,

but it's a special woven backing

that holds both roots and fibers together.

A network of subsoil pipes supplies the pitch with water.

Teo: The irrigation system is fully automated.

I have a computer system in the office

where I can do my work and control it.

I can have a remote to control it,

and as well as an app on my mobile phone,

that I can control it while I'm having breakfast, yeah.

Jin teik: In the past one year, it's been very positive.

We get definitely a sense of satisfaction,

of saying, okay, this strategy is working, it's coming along.

But then again, there is never complacency,

because we are dealing with a natural product here.

Narrator: The removable pitch is known as a lay and play surface,

and for the singapore stadium, it offers up an added bonus.

Teo: We have pretty much a multi-events calendar

where we've got sporting, we've got community events,

so because of this, the lay and play solution was approached,

and it works out very well for us.

Narrator: They can change the pitch in just 48 hours.

But whatever the event,

there's one issue that always needs addressing:

How to prevent spectators sweltering

in singapore's super-hot temperatures.

Narrator: Singapore lies just one degree north

of the equator, its tropical climate unforgiving.

Humidity is consistently over 70%,

and the temperature often soars

well over 80 degrees fahrenheit.

To avoid the spectator experience being compromised

by the extreme heat, the national stadium's engineers

must provide cooling on an enormous scale.

Flowers: Imagine the biggest room in your house,

we're talking about something thousands of times larger.

You know how hard it is to heat and cool that room.

Imagine trying to do it at a stadium of this scale.

Hutchinson: Quite clearly you can't condition the air

from the top and blow it down,

because it will just heat up again.

One of the essentials about any form of heating or chilling,

you don't want to heat or chill a space,

you want to heat or chill people.

Steele: Rather than air conditioning

the whole enormous volume of the stadium,

what the engineers came up with

was a per seat addressable system.

Narrator: Remarkably, cooled air is blown individually

to every member of the crowd from below.

Lewis: The air is being, is being pushed out

through, below the seats,

and you're getting the effect of that as blanket of cold air,

local to the seating tier,

not trying to cool the whole volume of the stadium.

Narrator: Pull out the seating,

and there is an intricate labyrinth of tunnels.

Ducts that send cool air

to outlets beneath every single seat.

Randall lim tse hsiang: So using the concept that hot air rises

and cold air sinks, we are able to keep the cool air

in the stadium by pushing through the seat outlets

and downwards to all the audience.

If you put your hand here, you can actually feel the cool air

coming out from the seats.

Narrator: It's a brilliant idea,

but the ducted air still needs to be cooled somewhere.

Lim tse hsiang: We have 160 air handling units

located at the back of house

that provide cool air to all the individual seats in the stadium.

Narrator: Warm air from the atmosphere

draws into these giant heat exchangers

where it meets cold water.

Lim tse hsiang: Behind me are the chiller plant room,

producing chilled water,

and once this chilled water leaves the plant room,

it travels through the pipes to the individual air chutes,

air handling units they're so called.

Narrator: The challenge here is how to produce

very large quantities of cold water on demand.

Steele: So one of the solutions they've come up with

is to use loads and loads of balls of glycol,

so basically antifreeze,

which you cool down to a very low temperature before a game,

and that means that you can use them to store up

all that cold in readiness for the big event.

Narrator: Glycol works like the ice packs

we put in the freezer; it retains cold.

Agrawal: The night before a big match,

they'll cool down the glycol,

which in turn can cool down the water,

and then this water will cool down the warm and humid air

which is then circulated out into the stadium.

Narrator: Once the cooling is achieved,

the water simply recirculates through the system.

♪ ♪

when the singapore national stadium was conceived,

one of the most demanding directives

was that it should be a multiple function area.

Like no other stadium on earth, it must host soccer, rugby,

cricket and athletics, as well as rock concerts.

Each kind of event needs a different-sized area,

but for all of them,

spectators need to be as close to the action as possible.

Steele: The only way to make sure people

are right at the forefront of the action

in loads of events with very different configurations

is to allow the seating stands themselves to move.

The first thing that happens is that middle tier retracts

downwards, and then the front tier of seats can move back,

covering those up and making a bigger space

in the middle of the stadium.

Lewis: There's 30,0000 seats that move.

In athletics mode, they drop down to the ground

and they're tucked under the retracted seats,

and there's about 5,000 seats that appear in football mode.

Narrator: The tiers weigh up to 1,500 tons each,

so this is an incredible feat of engineering.

Hidden underneath the seating bowl

is a state-of-the-art lift system.

Lewis: That's called a serapid machine.

It's a chain-driven machine that crawls around in a trench.

Narrator: With the help of this machine beneath the tiers,

the stadium's capacity transforms 50,000 to 55,000.

And for both configurations,

designers have maximized the spectator experience

by scientifically designing the acoustics.

Narrator: In public arenas, spectators demand excitement.

They want a high-volume assault on their senses.

Lewis: It's always about creating

the unforgettable experience for spectators.

In the singapore's national stadium we have achieved

something really special in terms of atmosphere.

Narrator: An important aspect of that experience

comes from the stadium's acoustics.

(cheering)

hutchinson: You want it to be noisy.

If you're cheering on the reds,

you want to hear everybody else cheer on the reds,

and the louder the noise, the better.

(cheering)

lewis: Acoustics are incredibly challenging,

because you're dealing with the different types of events,

so you're dealing with concerts,

you're dealing with soccer events.

You're dealing with different capacities within the venue,

so you have to design for absorption

on people being in the bowl, or how the sound will be reinforced

within that atmosphere.

Narrator: Here in singapore, sound engineers applied

rigorous science to the choice of materials for the roof.

Anything that would absorb sound, like soft curtaining,

was rejected.

Steele: You want to hear that crowd magnified, amplified,

and so in the singapore stadium they've got loads and loads

of highly sound-reflective surfaces that bounce that sound

back at all angles to try and make everything sound

as loud and intense and vibrant as possible.

Xu jingfeng: It's very important to have

lower part of the roof to be reflective,

which can reinforce this excitement

generated from the crowds.

Narrator: Today jingfeng is running a test to determine

if those reflective metal and plastic surfaces

are still performing as intended

throughout the stadium.

Jingfeng: We're going to play a special test sound

to check the frequency distribution

at each receiver location,

as well as how evenly the sound level is across the stadium.

The special sound that we're going to play is pink noise,

which is a flat sound across the overall spectrum.

Narrator: Pink noise is sound that's evenly spread

between low and high frequencies.

If the monitor shows a flat response,

it means the space is reflecting

all frequencies equally.

Any drop-off shows that frequency is being absorbed.

The results are all pretty flat.

Good news.

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(cheering)

when a stadium is at full capacity,

it is particularly vulnerable,

and that means crowd management has to be at the very center

of every design decision.

King: And when the game's done, everyone's out, you know.

So it's 55,000 people want to leave now.

Modeling that so that you understand

how people can do that comfortably and leave

and get to the various transport facilities

within a reasonable time frame and comfortable and safely,

is absolutely critical.

Narrator: The price paid when things go wrong

is the heaviest imaginable.

Agrawal: In a stadium, when it's full,

you've got tens of thousands of people

all in there at the same time,

and we know that we've had some really devastating disasters

in the past, whether it's hillsborough or heysel.

Narrator: At both tragedies, critical errors compounded

and people were crushed to death.

And if fire takes hold at a stadium

with poor exit planning,

the results can be equally shocking.

Hutchinson: And we saw that to our cost at the bradford stadium

where there was a terrible disaster,

about not being able to get people out.

King: Fires in these sorts of facilities are very, very rare,

but the history in the uk has shown that they can occur,

and understanding how people will react

and making sure that they can react and they can leave safely

in a very short period of time is critical as well.

Lewis: We've designed the building so that

the typical scenario is an evacuation in terms of a fire

or something which requires an immediate local response,

and for that we have an eight-minute time frame

in which we're allowed to take people from their seat

to a point outside of the stadium.

Narrator: Planning how 55,000 people can quickly evacuate

the stadium is a task where the architects couldn't afford

to make a single mistake.

Narrator: A life-threatening emergency at a crowded stadium

is one of the greatest fears for any architect.

Agrawal: So it's absolutely imperative that the design

of the structure and everything that goes around it

is really spot-on to make sure that we don't have

any devastating consequences from it.

Narrator: Singapore stadium's engineers used computers

to analyze crowd behavior

and help them plan entrances and exits.

King: These things are amazing to watch,

because you watch where people crowd and where they congregate

and where you're getting too many people,

where are the pressure points.

And it's really important to find where that's going to occur

and then change the design before you've built it.

Lewis: Part of the design of stadiums is around ensuring

that every exit, as you sequentially go to the outside

of the building, is getting wider,

so you're sequentially able to flow unimpeded at a faster rate

out of the building.

And a lot of that required us to make changes to the design,

because some of the widths, even 10-meter widths,

were required to increase to 12-meter widths

to allow for counterflow of people

under the cover of that canopy.

♪ ♪

narrator: The status of any stadium is defined

by the prestige of the events it holds.

One of the most impressive

staged at the singapore national stadium

was the 2015 southeast asian games.

King: That was a very successful event,

and it really showcased how the stadium can be best used

for those sorts of events.

That was something where the people of singapore came,

and really, I think, felt a wonderful atmosphere in here,

and, I mean, it's their city on display to the world.

Narrator: But in this day and age,

even a world class event is not enough to draw attention.

Flowers: Increasingly stadiums are urban projects.

They help give identity to cities,

and so therefore you want them to be prominent in the skyline

and prominent in the cityscape.

Agrawal: So for me the most impressive thing

about the singapore national stadium

is those plastic cushions at the top that light up

and just give the building a huge amount of personality.

Right at the crown, at the top of this beautiful dome,

is this absolutely startling feature

where they use lights to project images and videos

which you can see not only from the inside of the stadium,

but also outside from the city itself.

George michaels: The fact that we have a live roof

is very unusual, but it adds to the enhancement

of the patrons' experience, and this is what we aim.

We want to give the patrons, as they're coming in,

they can see a lit roof, and once they come into the stadium,

it's even a better experience for them.

King: When there's a goal and it says "score" and "goal,"

and it flashes from one side to the other,

and there's all this rock music and everything going on,

it just really pumps up the crowd,

and that's important for the stadium,

for the stadium to be successful,

but also how it's conveyed on tv for viewers at home.

Agrawal: So in order to create this really impressive display,

they've used tens of thousands of leds

on the retractable portion of the roof.

Narrator: The vast screen is one of the largest in the world.

And because it's made of leds,

it draws comparatively little power.

It's the final piece in this high-tech puzzle

and cements the stadium's high profile.

Not only is it the largest

free-spanning dome in the world,

it's prevailed against all its detractors

and become a triumphant

sport, entertainment and economic success story.

Flowers: Stadiums are so expensive,

in part because they are among the most profitable buildings

you can build.

Essentially a stadium is a machine for making money,

which is what we used to call skyscrapers.

But I really think stadiums have supplanted skyscrapers

as the penultimate--

no, the ultimate 21st century machine for making money.

Narrator: Against the odds, the singapore national stadium

has overcome the problems

of building on soft, reclaimed land,

it has a roof of unprecedented scale,

and extraordinary engineering enables its seating tiers

to be transformed on demand.

Jin teik: I think the emotional part is that it's come true.

It's a dream come true,

it is one that is, it will transform our lives.

Lewis: Just an amazing venue which we, as a team,

are just incredibly proud to see open,

and it is about an integrated approach to architecture,

design, with engineering, to achieve what we've achieved.

♪ ♪

♪ ♪

captioned by side door media services