Original subtitles

Narrator: How did a team of engineers

nicknamed the extreme team

build a futuristic research station

in the world's most extreme climate?

Man: This is a really savage environment

for any building to endure.

It's just really harsh out there.

You've got temperatures that go as low

as negative 58 degrees celsius,

and then you have wind speeds

that go as high as 160 kilometres per hour.

Narrator: How does this stunning visual trick

make a 3,500-ton concrete arch levitate?

Woman: It looks like the wing

is floating completely unsupported.

Narrator: And how did they build

the world's first rotating boat lift,

able to carry 500 tons of water and two boats

over 65 feet into the air?

Woman: All the falkirk wheel needs

is the equivalent power of eight boiling kettles.

♪

Narrator: This is the age of the extraordinary...

Man: This house always is on the verge

of falling down.

Narrator: Where ingenious engineers

have unleashed unchecked creativity...

Woman: Everything in this building

pushes at the boundaries of what's possible.

Narrator: Building structures so outrageous, they defy logic.

Woman: The forces on this thing

look like it should be torn apart.

Narrator: Now their secrets are revealed.

Discover the incredible stories of their construction...

Woman: These are extraordinary feats of engineering.

Narrator: To try and understand

how did they build that?

Imagine the engineering it takes

to build an advanced scientific research centre

that can cope with outside temperatures

of minus 58 degrees fahrenheit and house 60 people.

It has to be completely self-sufficient

for months on end

and be able to move locations quickly when danger strikes.

Debbie sterling: It's a brutal environment

for any building to survive in.

Narrator: But that's the building

the British antarctic survey needed,

a mobile research station that could survive

in the most hostile place on earth... Antarctica.

This ingenious series of rugged pods

uses train and space shuttle technology

so that top scientists can study our planet's atmosphere

all year round.

But designing something that could be built on a slab of ice

10,000 miles from home was a massive challenge.

Ellie cosgrave: The people who were building it

had to actually use electrically heated gloves

to counteract the frostbite.

Narrator: The crippling cold was only one of the hurdles

a dedicated team had to overcome to pull this off.

[Crunching]

Every part had to be delivered to an ice dock

that could crack open at any moment.

Snowdrifts would Bury the buildings and equipment

in the blink of an eye.

And the summer build season was so short,

it would take five years to complete.

The result was the extreme mobile research station

called halley vi.

So, how did they build it?

For the last 65 years, britain has been pioneering

the scientific study of the earth's atmosphere

in the most extreme environment on earth.

Joshua macabuag: This place has 1.2 meters of snow a year,

and the snow that does fall, it never melts.

Then you have the drifts.

This is a big wide-open space, so anything that you put there

is going to gather a lot of snow on it.

Narrator: Despite the tough conditions,

the clean air and low light pollution

are the reasons why the British antarctic survey

has been building research stations

in the antarctic since 1956.

In 1985, its scientists discovered a huge hole

in the ozone layer,

a finding that led to the global banning of cfcs,

reversing a potential catastrophe.

Named after the great astronomer Edmond halley,

the first four halley bases were simple structures

that worked for a while,

but always ended up buried deep under the ice.

In 1989, they upped their game,

building the fifth base on adjustable stilts.

Hugh broughton: So, halley v was quite clever

because it has these screw Jacks,

which meant the building could be jacked up every year

@by a meter or a meter and a half

to help it escape from the rising snow level.

Narrator: So halley v could move upwards to avoid the snow,

but there was a bigger problem it couldn't escape.

Every year the ice shelf it's built on

moves 1,300 feet closer to the sea.

Debbie: The halley v's legs were fixed into the ice,

and so they had to throw that design away

because there was a risk that the ice could break off

and the whole thing could just drift into the sea.

Narrator: It was time for a new, better halley research station.

Architect Hugh broughton Rose to the challenge

of designing a station that could overcome

the difficulties of being built and operating in Antarctica.

From the start, he faced an unusual set of limitations.

Hugh: Everything that needs to be delivered to halley

first of all gets unloaded from a ship onto sea ice,

and the maximum weight of component

could be no more than nine tons.

Then the other challenge is that this building

needed to be relocatable between 15 to 20 kilometres,

so quite a decent move.

Narrator: Being able to move the station

to avoid being stranded on an iceberg

topped the already formidable design criteria.

Some radical thinking was needed.

Hugh: The first thing we decided

is that we should come up with a modular solution,

so break the requirements of the British antarctic survey's brief

down into a series of interconnected buildings,

and the reason we did that is that those buildings

could be disconnected and moved more easily

from one site to another.

Nehemiah mabry: The modular construction is really fitting

for remote environments like this,

much likeúthe international space station,

where you can put things together bit by bit

without having to dig foundations

or anything that you would traditionally see

in a more reasonable environment.

Joshua: The eight pods, there's two sleeping pods,

two science pods, two generator and plant pods,

one command pod, and one double height living pod.

Narrator: Along with a team of expert engineers,

the architects created a blueprint

for what would be the most complete,

extreme environment accommodation ever built.

Eight individual pods would be linked

through enclosed gangways, like train carriages,

to create one integrated living and working organism.

To cope with the constantly rising snow,

huge hydraulically adjustable legs would allow it

to be raised and lowered,

and each leg would sit on a massive teflon-coated ski.

If danger threatened, each module could be detached

and moved to a new location,

where the station would be reconnected,

avoiding a catastrophe.

The modular plan solved many of the problems

the extreme environment presented,

but there was no getting away

from the greatest single challenge

facing its construction,

the extremely short summer building season

of just 12 weeks between December and February.

Hugh: The construction season in the antarctic

is unbelievably short.

Days in January and December, which might be minus 5,

suddenly at the end of February, beginning of march,

you're working at minus 25,

and that's pretty hardcore if you're working outside,

so then you've got to leave your site

for the following 10 months, until you can come back again.

Narrator: While the construction crew could fly in

on a Russian transport plane,

all their tools and supplies had to be delivered by ship.

The logistics here were tough enough,

but it was that short three-month window

when external work was possible

that meant a traditional approach to construction

was impossible.

Hayley loren oakes: The only really sensible solution

was to prefabricate everything in a warm country,

in this case, South Africa.

Narrator: To maximize efficiency,

the engineers test-built two complete modules near Cape Town.

This meant they could perfect components

and train the construction team

before shipping all the parts 4,300 miles to Antarctica.

Hugh: The buildings were built as in a kind of kit form,

and that's because it's hard to move things

when the ship arrives at the edge of the sea ice.

Narrator: The on-site build began in 2007.

Icebreaker ships had to straighten

the edge of the ice shelf.

Once in position, everything was unloaded at breakneck speed.

The planning had been meticulous.

Hugh: We wanted to be able to unload components,

for the components to be as big as possible

within that weight restriction of nine tons,

and for all the parts to be able to click together

as quickly as possible.

The biggest part that we made was the steel frame,

which forms the base of each of the modules,

which is basically a whole series of tubes joined together

in a three-dimensional form to maximize strength

and making it easier to move from the ship

to the building site.

Narrator: For seven days,

caterpillar tractors worked nonstop,

pulling 500 tons of cargo 7 1/2 miles inland,

to the still-functioning halley v base.

The result was an extraordinary collection

of prefabricated components awaiting assembly on the ice.

Joshua: Everything was arranged in a very well-organized,

very well-labeled line, four kilometres long.

Narrator: The plan was to get each module on its legs

and with all the key components fitted before winter arrived,

which would shut down the site until the following year.

The construction crew of 40 men,

who lived in prefabricated huts near halley v,

worked in shifts around the clock to stay on schedule.

Hugh: In order to maximize

the efficiency of the construction process,

we approached it in the same way almost that you would

an assembly line for making a car or something like that,

so we had one crew doing steel frames,

another crew building shell.

Joshua: Given the dangers of being in the antarctic

and the limitations on space,

all of the builders had to be able to do more than one job.

Hugh: There would be a team

installing the primary building services,

things like the generators, the sewage treatment,

the water production unit,

and then the service connections that go between the modules.

Joshua: These were definitely no ordinary builders.

In fact, they were nicknamed the extreme team.

Man: Behind me is the second energy module

with all the plant and equipment placed upon the floor deck.

The obvious ones to point out

are the big pink tank at the back, which is fuel,

and the big grey tank at the front, which is water.

Narrator: Every single unit that could be pre-built

before arrival had been.

Man: As you can see, there's the prefabricated bedrooms,

plant room, and wc.

Next stage for this is to have

the structural steelwork erected around it.

Hugh: The bedrooms had the beds in, the desks in, the wardrobes.

We didn't go as far as putting the duvets and the pillows on,

but it was pretty close to that.

Narrator: By the time the extreme team

had the pod frames on their legs,

with the key components fixed inside,

the days were becoming very cold and short.

It was time to wrap the structures

and prepare the site for the bitter winter to come.

They could only hope

the equipment and materials would survive.

Hugh: So, if you're going to leave

any of your equipment there,

you need to make sure that it's durable enough

to withstand the harsh antarctic winter,

and that was a hard thing to do.

There are materials which are used

in food cold stores and things like that,

but they typically go down to minus 25.

But to say to someone,

"oh, no, your product's actually going to go down to minus 55,"

that's sort of a different level.

Narrator: During testing off-site,

the module cladding was found to be too brittle.

As a result, no work was done in the antarctic

the following summer season,

while the materials were perfected in South Africa.

Finally, 21 months after wrapping them up,

the extreme team returned,

and the half-built modules were released from winter's grip.

Man: Ok, so here we are on the halley vi site,

and these structures are going to be towed up a ramp,

and the snow height here is about 20 foot at the back,

so we'll clear it out, make a ramp,

tow the structures out, and take them to the south.

Narrator: Cladding the modules was next.

It was these improved panels

that would give the halley vi pods their distinctive shape,

a look inspired by a 50-year-old kids' TV series.

Ellie: I can totally see this in the design,

but apparently the architects and the engineers

for this project were inspired

by the sixties puppet show "thunderbirds."

Hugh: I was a massive fan of the thunderbirds.

I think the influence is pretty clear,

and thunderbird 2 was coursing through the design from day one.

Narrator: The thunderbirds-inspired pods

wouldn't just look good.

Crucially, they would be the first line of defense

against the harsh weather for everything and everyone inside.

Hayley: The walls are made of glass-reinforced polymer,

or grp, and more commonly known as fibreglass.

It's 75 percent lighter than the steel equivalent,

and it's super strong, and it's lightweight,

and it can actually resist corrosion,

and best of all, it's a brilliant insulator.

Narrator: Although fibreglass was known to be tough,

Hugh needed to be sure it would survive

the antarctic conditions.

Hugh: When we were having

the glass fibre shell manufactured,

we went through a really rigorous process of testing.

We subjected it to the effects

of the ice being blown in the wind,

so we blasted it with sand to simulate that.

We sprayed water at the cladding material,

or the building shell material,

and then lowered the temperature really quickly

to see what happens under freeze/thaw kind of cycles.

Narrator: The glass fibre cladding,

backed by 12 inches of high-performance insulation,

would protect the researchers from the cold,

but there is another extreme

from which people here need protection...

The light or lack thereof.

Hugh: We decided that at the heart of the station,

in the main big red social module,

it'd be really great if we could have

a big double-height space with a big window

because you just get really nice light

in the antarctic in the summer,

and it would just provide a really great social focus

for the community.

But of course, the big challenge you have in the antarctic

is if you create a big window,

then it's also a source of massive heat loss potentially,

so we, we really searched high and wide around

and discovered this incredible material

that was invented by NASA, called nanogel.

Narrator: Nanogel was used on the space shuttle nose cone

to protect it from the extreme heat of re-entry,

but it is equally effective at protecting from extreme cold

and also happens to be translucent.

Hugh: Around 50 percent of light is actually transmitted

through this material,

so we have this big window at the heart of the station

which allows lots of good natural light in

without letting lots of heat out of the building.

Narrator: With 1,300 feet of the ice shelf

flowing out into the sea every year,

by December 2011, the third season of the build,

it was time to tow the modules nine miles inland from halley v

and the ever-approaching edge.

But by now, with modules fully built,

even the smaller blue pods weighed as much as 100 tons.

Ellie: The biggest challenge to getting the pods

to their new home over the last 15 kilometres

was overcoming something called stiction.

This is the static friction that needs to be overcome

to get objects to move.

Narrator: The designers turned to a very common material

found in almost every kitchen.

Hugh: The skis are made out of high-grade steel

that's suitable for a cold environment,

and then they have a layer of teflon,

which is essentially fixed to the underside,

to help them to glide across the ice.

Narrator: The skis were so effective,

the extreme team had to make sure

the 100-ton pods didn't run out of control.

Man: Stage two. Last night, it was pulled off

the construction line at this end,

turned round, and a few tests done on it.

What we're interested in is how slowly can we tow it,

how easily you can control it, and how quickly you can stop it

or what the stopping distances are

because when we get to the other end,

they will have to be a certain distance apart.

Narrator: Twice the size of the blue modules,

the red command module proved much harder to move.

Man: We're definitely over 200 tons with it,

so it's out of our comfort zone slightly,

but a good team on the job.

If anybody can shift it, we can.

Operator: Ok, on the count of 3.

♪

Narrator: Moving the eight modules

the nine miles took days,

and as each module arrived to meet its new next-door neighbour,

they were introduced with a bang.

[Bang]

The connecting gangways proved to be resilient components.

Ellie: They connected the pods using a double-layered version

of the kind of concertina connections

that you see in many railway carriages.

Hugh: They're insulated when they're used

in the Scandinavian countries, so again,

it's normally used in the rail industry,

but we just transferred it over to our buildings.

Narrator: Finally, all eight modules were linked and sealed

from the weather.

The only exterior connection was a safety gantry,

an intentional firebreak to protect

one set of modules from the other

in the event of a catastrophic fire or explosion.

The last job of the year was to prepare halley vi

for the next blast of winter.

Hugh: Because the snow level is constantly rising,

what you do is that each leg in turn,

you lift it up, using the hydraulics,

you push snow underneath

to make a platform of around one to one and a half meters,

and when you've done all of the legs,

you then use the hydraulics again to Jack the building up

so it's sitting on these snow platforms

well above the surrounding ice level,

and then when it snows

and the wind blows snow around over the winter

and the level rises by one and a half meters,

it brings the whole thing kind of up to a level again.

Narrator: In February 2012,

over five years after the build began,

halley vi came into service

as the British antarctic survey's new research base.

Its 60 occupants had never known such luxury.

Nehemiah: If you're going to do research

and you're going to live in one of the coldest places,

if not the coldest place on earth,

then the least you can do

is have a really cool place to chill in.

Narrator: Halley vi is without doubt

the most complete extreme environment

accommodation ever built,

but in the antarctic,

mother nature takes no prisoners.

In 2016, a huge new 500-foot-deep crack

appeared in the ice shelf.

Just 18 miles from halley and moving fast,

it posed a grave risk to the station and the team.

Hugh: This crack was discovered on the 31st of October 2016,

so it's known as the Halloween crack,

and it was moving at some speed,

and so they then took the decision

that because there was one crack going in one direction

and another at 90 degrees,

that the new site for halley vi had become far more dynamic

than they had originally envisaged

and there was risk of leaving people over a winter

of not knowing how those two cracks would interact.

Narrator: They decided to act.

It was time to test out halley vi's built-in mobility

and move the base to safety and a new site inland.

It was a timely reminder of how brilliant engineering and design

can make the impossible possible.

Hugh: You know, somebody living

in an antarctic research station,

you know, their life is at risk constantly

because of the extreme environment,

so you need to think of every single situation.

You know, building a research station in the antarctic

is equivalent to building a formula one racing car,

and, you know, you just can't leave anything to chance.

You know, there are a number of parameters

that you have to design within,

and you have to give each of them a great deal of respect

because failure to do so will be catastrophic.

♪

♪

Narrator: 5,900 miles north of the antarctic circle,

just off the coast of Morocco, are the Canary Islands.

With year-round sunshine and warmth,

buildings here have no need

to protect their occupants from harsh weather.

Instead, they can be built

purely to celebrate their surroundings and purpose,

which is exactly what this incredible concert hall

was built to do.

Its 426-foot-long, 3,500-ton arch

is engineered to hover above the auditoria below.

Ellie: It's an incredible optical illusion.

It looks like the wing is floating completely unsupported.

Corina kwami: It's the improbable

made to look impossible.

Narrator: Inside is a stunning space

for over 2,000 music lovers,

but it's outside where the building hits the high notes.

The incredible 190-foot-tall arch is only possible

thanks to a secret skeleton of hard-core steel.

The concrete cladding that creates its skin

was so pioneering, an extraordinary new machine

had to be custom-built to make it.

Curved walls glisten

with over three million tiny handmade tiles,

and the giant wing flexes in the powerful wind.

Auditorio De tenerife

is a stunning engineering performance.

So, how did they build it?

In 1997, work began on a new concert hall

in Santa Cruz De tenerife in the Canary Islands.

Spanish modernist architect Santiago calatrava,

who'd recently finished the awesome oculus transport hub

in New York's trade centre,

had designed a building that could match any music venue

in the world for visual drama, both inside and out.

His design of flowing forms

performing impossible engineering gymnastics,

all clad in seamless concrete,

would be one of the greatest construction challenges

of its time.

The most difficult to build

would be the three curved components

at the heart of the structure.

Each would have a nickname.

The nut would be the 147-foot-high central building

to house the two performance auditoriums.

It would also provide a single point of crucial support.

The nut would be flanked by the two sails.

The curving slabs are actually the outer walls

of the main concert hall.

On top is the wing.

This massive structure, weighing the same as ten 747 aircraft,

would be made of a steel frame,

clad in a thin layer of ingeniously cast concrete.

It would rest on that small point of support

provided by the nut.

Debbie: To create a structure like this,

there is no off-the-shelf solution.

You have to create something entirely from scratch.

Narrator: The bespoke building technique

that was key to the creation of the auditorio

was the concrete formwork that produced its cladding.

Joshua: The simplest form would be to take two wooden boards,

support them in place,

put reinforced concrete in the gap in between,

fill it all with concrete, let it set,

and take the boards away, and you've got a wall.

Narrator: Concrete formwork can be used

like blocks to build walls,

one layer added on top of another,

as many times as the steel reinforcing inside allows.

Stacking layers like this is how engineers virtually hand-built

the huge concrete walls of the sails,

but the massive arcing wing

would present a completely different challenge

and a solution that was a world first.

By 2001, the nut and sails were structurally complete.

It was time to build the giant wing.

Like the sails, the surface of the wing

would be concrete formwork,

but hidden inside would be the heavy-duty engineering

that made this outrageous shape possible.

A huge steel framework was prefabricated in Spain

and shipped in 17 pieces,

before being assembled into larger sections on site.

Juan Carlos was the site engineer.

Juan Carlos ramflo ramos, translated: Each piece weighed

around 200 to 250 tons.

They were lifted with a crane, and once they were up,

a system put together the mobile and the fixed part,

welded it, and then let it go.

It's unique.

Corina: You have a steel skeleton

that was constructed to give the whole thing

a rigidity and strength, 24 rows of beams.

Narrator: Once the steel frame of the wing was assembled,

scaffolding was built under the inner areas

to support traditional wooden formwork molds.

But using formwork to make the concrete outer shell

on the huge areas of the wing was not an option.

The scaffolding required to work at such heights and angles

would have made the build impossibly slow,

complex, and expensive.

These problems meant the construction company

had to come up with something special.

[Speaking Spanish]

Juan Carlos: With the wing, the big curve,

this was such a complex process of engineering

that they had to design a special machine

to put the iron and the concrete in,

and this was supported by the same steel wing.

It's unique and was built especially to do that.

Narrator: This machine is called a carriage crane.

It was assembled on the back of the wing,

and its huge arms wrapped around and underneath

to support the formwork.

Adjustable in every direction and guided on huge rails,

it enabled concrete to be attached along the wing

in previously unreachable places.

Hayley: This was a very slow process to create the wing.

@they had to align the formwork,

pour the concrete, let the concrete set,

then move the machine up and realign the formwork

in a different, narrower shape and a different angle,

and then re-pour the concrete and let it set

and repeat that 32 times.

Narrator: The final result is an extraordinary fluid shape

that, despite weighing 3,500 tons, appears to levitate.

Debbie: This is an amazing optical illusion

because when you look at it, it just looks like this wing

is just completely floating in space,

but from certain angles,

you can see behind the smoke and mirrors.

Narrator: The wing is supported at just five points,

an amazing feat considering the powerful winds

that almost constantly sweep across the Canary Islands.

But one of these supports

is a special, steel, shock-absorbing tube

that moves up and down with the wing

to stop it from tearing itself off the building.

Ellie: In really high winds,

you can hear it just bouncing up and down,

which I'm sure sounds pretty terrifying,

but I'm sure they knew what they were doing.

Narrator: The auditorio's architect, calatrava,

wasn't satisfied with just making the concrete

achieve impossible shapes.

He wanted his building to have an outstanding surface as well.

The concrete was mixed with a high proportion

of sand and titanium dioxide to brighten it almost to white,

but calatrava wanted more.

To make the building gleam, he wanted it covered

in 3 1/2 million tiles,

all hand-laid in a style called trencadís.

But surely, even on this project,

that was too going too far.

@miriam Gil: Basically trencadis means broken ceramic tiles

all together on the same work, right?

Anyway, mosaics is good, and I will show you,

@they're one-square-meter panels

that came pre-madeúon a flexible net from valencia,

with different numbers.

You can see like a wave, a zigzag curve, right?

Can't you?

And just one meter up, there is another one here.

Right? And there is another one over there.

Once you have this information,

you can see the different levels of the surface.

We have made a Jigsaw puzzle here.

Juan Carlos: Truly, the only word that comes to mind

is spectacular.

The effect you get when the music plays,

something that truly transports you.

Narrator: Close inspection may reveal a small cheat,

but stand back, and its full effect is plain to see.

It all adds to create a glistening introduction

to a music lover's evening.

♪

In Scotland, in the mid-1990s, an audacious plan was hatched

to reconnect two of britain's most historic canals.

They were only 980 feet apart,

but one was almost 80 feet higher than the other.

For waterways that were once

the superhighways of the industrial revolution,

that is worlds apart.

But an effort to reconnect these two canals

overcame the huge problem, with an engineering solution

of stunning simplicity and efficiency.

Hayley: This is the only Ferris wheel boat lift

in the world.

Narrator: This is the falkirk wheel...

A fusion of sculpture and engineering,

breathing new life into a historic canal,

and now a tourist destination in its own right.

The wheel can effortlessly lift nearly 500 tons of water

and two boats 78 feet,

while not spilling a drop or breaking a sweat.

So, how did they build it?

250 years ago, these narrow channels

helped transport goods around the country,

fuelling britain's booming economy.

Here, the beautiful union canal

runs to Glasgow in one direction,

and the forth & Clyde canal runs to Edinburgh in the other.

Corina: These canals were the lifeblood

@connecting Edinburgh and Glasgow

during the industrial revolution,

and it also provided a luxury high-speed service,

the bullet train of its day.

Narrator: The waterways were completely reliant

on a system of locks, which allowed these two canals

at different heights to be connected.

But by the late 1800s, trains were all the rage,

and the canals and crucial lock system between them

were barely used.

Corina: Due to the height difference

between the forth & Clyde and the union canals,

11 locks were needed to get the boats from one to the other,

but these fell into disrepair in the 1930s.

Narrator: Not surprising when you consider

that taking a boat through these 11 locks

took almost an entire day.

Eventually, they were demolished,

and the stretch of locks and the waterway between them

lay unused.

Glasgow and Edinburgh were no longer connected by canal.

Tony kettle: It was broken, fractured you might say,

during the 1960s and '70s, úwith roads and other obstacles.

Narrator: By the mid-1990s, canals were back in fashion,

now used for pleasure rather than industry.

British waterways wanted the old route restored.

To join the canals,

they would have to dig

a new canal,

but overcoming a massive height difference was tricky.

Rebuilding the hopelessly slow staircase of locks

that once connected the two canals at different heights

was not an option,

so in the mid-1990s, the search for a modern solution began.

The design that was given the go-ahead

was a completely original concept.

Tony: This is the world's first rotating boat lift

that can take boats in a circular direction

from one canal to the other.

What we've created here is a piece of sculpture

that becomes a landmark and a destination for Scotland.

Narrator: The falkirk wheel is a 200-ton steel Ferris wheel,

with two gondolas, or caissons,

pivoting around a giant central axle.

The caissons act as huge buckets that hold water and the boats.

The wheel turns, moving the boats and 500 tons of water,

to connect them 78 feet above or below to the other canal.

At the top, it's all connected by an aqueduct

that would have done the romans proud.

The romans would prove to be this project's first obstacle.

A Roman earth fortification once stood here.

Today, all that's left is a grassy hill.

But 2,000 years ago,

it was the northernmost border of the Roman empire.

Jim Steele: Where we stand is

a unesco world heritage site,

which is the antonine wall

and that was built in a.D. 142,

so we had to actually get the canal

underneath the antonine wall, through a tunnel...

@the tunnel was about 200 meters long, 8 meter in diameter...

On to the north side of the antonine wall,

extend it on to an aqueduct

and then on to the falkirk wheel.

Narrator: Digging a 650-foot tunnel under the antonine wall

was achieved without drama.

Building an aqueduct 80 feet high over the basin

was a more serious challenge.

Jim: If you had been here 20 years ago,

what you would have seen is a whole forest of scaffolding.

So, everything was supported by scaffolding,

so it basically takes a small part of the load

of the wet concrete as you're pouring it

and as the four piers are poured,

the gap to the deck itself,

that's all supported and all constructed in four sections.

Narrator: No one had built a canal in Scotland

for 200 years.

That lack of practice initially caused a few more problems.

Jim: Inevitably there were some leaks, not in the structure,

I would have to say, but in actually the earthworks

approaching to the viaduct.

But over a series of a few weeks or months, you know,

we actually plugged all the gaps

in the waterproofing of the canal.

And then on we go, and to my knowledge,

it's never had a problem in the 20 years since it's been open.

Narrator: With the forth & Clyde canal

connected through to the aqueduct,

the wheel itself could be installed.

This system required trapping

250 tons of water in each caisson

and moving one up and the other down

78 feet to the basin below.

To engineer a structure able to carry 500 tons of water

on the end of two steel arms

while keeping everything steady and under control

meant relying on some key laws of physics.

Tony: It's like a balanced beam,

and that weight really means it's very, very efficient,

and the water and the boat balances out,

so we had this unique balanced beam idea,

that I don't think there's another boat lift

that uses that principle.

It uses other elevator-type principles

with weights and things, but not a balanced beam,

which is the fundamental system here.

Narrator: The natural balance of having equal amounts

of water at each end makes sense,

if both caissons are holding boats.

But how does the falkirk wheel stay balanced

if it's only transporting one boat

and the other caisson is empty?

To answer the question,

engineers made clever use of the Archimedes principle.

Tony: Archimedes had a Eureka moment

when he realized that if he put an object in his bath,

the weight of the object

was displaced exactly with the water,

and it's the same principle here.

Nehemiah: So, in this case, as a boat floats into the chamber,

it's going to remove the exact amount of water

that's equal to the weight of the boat,

so that means that as long as you keep

the water levels the same,

it's going to continue to weigh the same

with or without the boat.

Narrator: Now, the massive payload needs to be rotated.

@hayley: Normally moving 500 tons of water 24 meters in the air

@takes the same amount of energy

as a typical Scottish household over three days,

but all the falkirk wheel needs

is the equivalent power of eight boiling kettles.

Narrator: The balancing act means the wheel is easy to turn.

As the wheel lifts one tank,

the downward force of the tank on the other side

does most of the work.

Like a seesaw, water keeps the wheel balanced,

but it creates another problem.

Each massive tank contains 66,000 gallons,

and if this water starts sloshing from side to side,

there could be trouble.

Corina: The biggest problem is the water.

You have to keep the gondolas, or the tanks, level.

Plus, when you start to move water,

it creates a critical mass that's really hard to stop.

The entire structure could tip over

if it's not carefully controlled.

Tony: We had to solve the problem of how to stop the water

from making the caissons turn over

because as you move them round, they're inherently unstable.

You know, if you take a ferry full of water

and the water flows from one side to the other,

you know, it's very difficult to control it

once it starts to move.

Narrator: The best solution proved to be the simplest.

Tony: It's connected by a simple system of cogs and wheels,

and we have five cogs, of which the central one's fixed

and the outer two are fixed to the caissons,

and then the two wheels in between

are allowed to freely move around,

and what they do is they allow caissons

to always remain horizontal,

no matter what forces are applied

to the two beams going around.

Narrator: As the wheel turns, the central axle drives cogs

that run up the arms of the wheel.

These are geared to create an always-correct connection

to the caissons,

which stops any internal force affecting their position,

prevents the caissons from swinging out of control,

and keeps them permanently level and safe.

The falkirk wheel is the perfect marriage

of beautiful design and clever engineering,

reconnecting a historic canal route

with a uniquely modern solution.

Hayley: The finished wheel is a piece of pure engineering

meets Celtic sculpture,

providing a breathtaking example

of how human problem-solving can achieve the spectacular.

Jim: It's still very well-attended,

it's one of the main tourist attractions in Scotland,

and it actually sits as an iconic structure

within all the other iconic structures

that have been built in the UK and in Scotland.

And again, very proud to have been part of the team

that actually delivered this.

Tony: It's in the British passport, you know,

it's on the Scottish pound note,

and it's really great that something of today

that takes old technology and reuses it in a different way

and is innovative in the way it approaches things

and is actually celebrated,

and I think that's the best thing of all, you know.

If people can enjoy and know that there's a future

and there are more things to be discovered,

@that's the most exciting thing.

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