Original subtitles

[Narrator] Adrift from the US Mainland,

a desert Island with an infested past.

[woman 1] In every direction, you see nothing but ocean.

This place is truly far out,

but the importance of this site cannot be underestimated.

[Narrator] The brutalist palace a dictator once called home.

[man 1] When it was completed, the ruler of the country

decided he liked it so much, he was going to keep it all for himself.

[Narrator] And the colossal wartime project

[Narrator] And the colossal wartime project

the Nazis thought no one knew about.

[man 2] The British did something very smart.

They let the Germans keep working on it.

[Narrator] Decaying relics.

Ruins of lost worlds.

Sites haunted by the past,

their secrets waiting to be revealed.

[Narrator] Far off the southern tip of Florida is a ruin lost at sea.

[man 3] So most people think that Key West itself is remote,

but this place, this is even further remote than that.

[woman 2] Though this is, technically, part of the US,

it feels like you've dropped off the map.

[Narrator] Marooned on a small island,

its appearance on the horizon comes as a surprise to most.

This place is really a mystery,

because it's this huge pile of brick and mortar masonry

in the middle of the Gulf of Mexico.

[man 3] When you first see this place,

as it rises up out of the ocean,

you can't help but feel amazed and in awe,

but a little spooked.

[man 4] It's weathered the storms of decades,

or perhaps centuries, but still standing strong.

or perhaps centuries, but still standing strong.

[Narrator] Distinctive features betray some of the sites' secrets,

but others remain hidden.

This place looks like a fort, but that's not all it was.

This was not somewhere you wanted to end up.

[woman 1] For some of the people who were sent to this island,

it would become a deadly, deadly place.

[Narrator] A vast abandoned structure emerges from the ocean,

[Narrator] A vast abandoned structure emerges from the ocean,

70 miles beyond Key West.

Adam Hollywood has been making regular trips out here for almost 20 years,

and knows the lay of the land better than most.

This is end of the barrier recess,

and it runs all the way from Miami

out here to the middle of the gulf.

It creates the choke point for the entire Gulf of Mexico.

So, any large ships, they would have to sail to the south of us,

and then up into the Gulf of Mexico.

When this place was built,

the primary concern was piracy.

the primary concern was piracy.

The United States was interested in protecting shipping

along the American coast and in the Caribbean.

And so, this provided a strategic location to police these waters.

[Narrator] Piracy may have been the impetus for building here,

but pirates weren't the only threat.

[man 4] Ever since the war of 1812,

when the British threatened to cut off trade,

the Gulf of Mexico became a strategically vital place

for the New United States of America.

for the New United States of America.

[Narrator] This dominant military position

is Fort Jefferson.

Construction began in 1846.

Initially, slaves were forced to carry out much of the heavy lifting,

but details across the site show

that change was on the horizon.

This place is absolutely enormous.

But if you look closer,

you can also see some irregularities.

Some of the bricks are different colors.

Some of the bricks are different colors.

[Narrator] In 1861, the American Civil War broke out.

Remaining in union hands,

this island, now, became a potentially decisive position

from which to blockade the South,

if they could get the fort completed.

[Hollywood] First two tiers are made up of a light tan or sandy colored brick.

And all those bricks were coming from Pensacola, Florida.

But when Florida joined the Confederacy,

they stopped sending bricks from Florida.

they stopped sending bricks from Florida.

So then they had to start getting bricks from Brewer, Maine.

So when you look at the third tier of this fort,

you'll see that the bricks are much darker, redder looking bricks.

[Narrator] Following the Emancipation Proclamation,

the Union needed to find a new workforce.

The site's location made the choice of whom to employ easy.

[Gutierrez-Romine] Another thing with this island that was really important,

was its isolation.

And that made it ideal for a prison.

And that made it ideal for a prison.

[woman 1] In this case, Union deserters would be sent down there.

Lincoln would have them form a really crucial body of workers,

who would do all sorts of tasks on the island.

[Narrator] While technically,

the fort was still not complete,

soon, enough was built to make it ready for war.

[Hollywood] From this fort here, Fort Jefferson,

as well as Fort Zachary Taylor in Key West,

the ships that worked out of these harbors

were able to capture over 300 shiploads

were able to capture over 300 shiploads

of supplies, that were going to the South.

[Narrator] While Fort Jefferson left its mark on the civil war,

one prisoner would come to leave their own imprint on the tail of this fort.

[Hollywood] Samuel Mudd was the most famous prisoner we had here,

in the Dry Tortugas at Fort Jefferson.

He was convicted as being a co-conspirator

in the assassination of President Lincoln.

[Narrator] April 14th, 1865.

In the final days of the civil war,

In the final days of the civil war,

President Abraham Lincoln attends a performance

at a theater near the White House.

While he's watching the show,

an assassin enters his box,

shoots him in the head from behind,

and then to escape, leaps out of Lincoln's box,

catches his boot in some bunting coming down, breaks his leg.

[Narrator] On the run, the assassin, John Wilkes Booth,

calls in at the house of Dr. Samuel Mudd,

who sets his leg.

who sets his leg.

Mudd, however, fails to alert the authorities.

Two days later, suspicion of Mudd's complicity are raised.

It proved enough for a conviction.

Samuel Mudd himself, he was sent here

to the Dry Tortugas at Fort Jefferson to do a lifetime of hard labor.

[Narrator] Mudd quickly learned this would be no easy ride.

[Wawro] Tourists pay good money to come to places like this nowadays,

because of the beaches, because of the sea, the sun,

because of the beaches, because of the sea, the sun,

but nobody wanted to go to Fort Jefferson during the American Civil War.

It was, basically, a one-way ticket to death.

[Narrator] Danger lay in the most basic struggles to survive.

[Mitchell] One of the absolute challenges,

in a site such as this one,

would be the matter of fresh water.

[Narrator] Clues in the cells show the lengths the inmates would go to,

in order to combat this situation.

in order to combat this situation.

[Hollywood] They actually dug trenches out in this cement floor,

and then bowls that would help store the water.

And so, you can see even today,

we had a little bit of rain last night,

and these trenches help fill up these bowls of water.

So these were just to help give the prisoners enough fresh water to survive.

[Narrator] A large desalination system was installed,

to provide a steady supply of drinking water.

But the storage of this water in barrels

would, inadvertently, have deadly consequences.

would, inadvertently, have deadly consequences.

[Mitchell] Something happens that

is going to drastically change things for Mudd in prison.

It's going to completely change the trajectory of his experience there.

[Narrator] In the 1860s,

Dr. Samuel Mudd was sentenced to a life of hard labor, here, at Fort Jefferson,

where an attempt to provide drinking water

was about to turn sour.

On August 18, 1867, a prisoner became ill.

And within a short time, over 30 people would fall ill

And within a short time, over 30 people would fall ill

on one single night.

[Narrator] Fort Jefferson had been hit by an outbreak of yellow fever.

[Mitchell] This incredibly violent, horrible disease,

that could make people so deathly ill,

it causes the yellowing of the skin, jaundicing. That's why it's yellow fever.

[Narrator] Before long, the fort's doctor succumbed to the disease.

Suddenly, responsibility for the sick fell to Dr. Mudd.

It's been reported that he utilized the fort's design to aid his efforts.

It's been reported that he utilized the fort's design to aid his efforts.

[Gutierrez-Romine] Yellow fever is a viral disease,

that is spread by mosquitoes.

Their collection of water that they had desalinated,

had actually been a breeding ground for mosquitoes.

And so, that was really the heart of the problem.

This hallway that was actually designed to help create a breeze

to vent out the smoke and the heat from the cannons,

that would have been in these rooms.

that would have been in these rooms.

One of the things that Samuel Mudd did realize

is that bringing people up onto the second level of the fort

seemed to reduce the number of people that were getting sick, here, at the fort.

The fact is, mosquitoes, they tend to stay low to the ground.

They don't fly into a lot of strong wind.

[Narrator] Alongside this,

Mudd introduced far stricter hygiene procedures,

when dealing with the patients.

And it worked.

Mudd's efforts saved many lives.

[Mitchell] From his heroic efforts, Mudd was granted clemency,

[Mitchell] From his heroic efforts, Mudd was granted clemency,

and he was freed.

He went home on an appropriately named ship, The Liberty.

[Narrator] Once home, Mudd resumed his own medical practice,

where he worked until his death, in 1883.

Fort Jefferson itself was never completed.

In a rapidly changing world, it had been abandoned in 1874.

[Narrator] Today, the Fort and surrounding islands

[Narrator] Today, the Fort and surrounding islands

are under the authority of the National Park Service.

[Mitchell] It's a wildlife refuge,

that not only enables people to enjoy the nature,

but also to have an appreciation

of an unexpected history in an unexpected place.

[Narrator] In Bulgaria, a sprawling site hides in the foothills

of the Lyulin Mountains.

of the Lyulin Mountains.

The area is very famous for mineral springs,

where people would go to recuperate.

It was a place for relaxation, for important people, for people of means.

[Narrator] Traces of luxury litter this site.

The architecture, it's a mixture between stark and ornate.

It's got this kind of grandiosity of the place.

It's got this kind of grandiosity of the place.

[man 1] This is strange, when you consider the country's past.

In recent years, it wasn't a place known for its wealth.

[Narrator] This extravagant resort is conspicuous in design.

Yet there are no signs to it,

and it's buried deep in the woods.

[woman 3] Why build something this showy, and then hide it?

[Narrator] Architect Iliyan Nikolov

[Narrator] Architect Iliyan Nikolov

worked on the construction of this building.

He hasn't been back here for 40 years.

[translator speaking] Now, it's all coming back to me.

This part was an extension to the building.

[Narrator] Iliyan worked here in 1978.

His father, Pavel, designed this place.

[translator speaking] In my hands,

I have an original sketch of this building,

dating back to 1972, and drawn by my father.

dating back to 1972, and drawn by my father.

[Narrator] The costly finish on its now crumbling facade,

suggests that this building was designed to be special.

[translator speaking] Making this rounded stone cladding,

decades ago, was a near heroic achievement.

Look at that. This thing here.

Now, this is indeed a very emotional moment for me.

This rotting door,

which is very typical of this building,

which is very typical of this building,

with its rounded shapes at the top and the bottom,

this was my very first ever professional, commissioned project,

after my graduation as a qualified architect.

[Narrator] The story of this dilapidated site

dates back to the aftermath of the Second World War,

when Bulgaria fell under the influence of Stalin's Soviet Union.

[Narrator] By 1954, the communist leader, Todor Zhivkov

[Narrator] By 1954, the communist leader, Todor Zhivkov

had taken charge.

Todor Zhivkov was trusted by Stalin

and by subsequent Soviet rulers,

because he was a yes-man.

[Narrator] Zhivkov's loyalty meant that by the 1970s,

he was still in power.

And he gave his approval for construction at this site in 1973.

And he gave his approval for construction at this site in 1973.

It was intended as a holiday spa complex,

where deserving, hard-working, party members could come

and recuperate in the region's healing waters.

It's now known as Bankya Residence.

Iliyan remembers its grand design.

[translator speaking] We are currently down in the main lobby,

which was quite lavishly furnished.

There was a resting area, right here,

directed towards the park.

directed towards the park.

Behind the corner is the dining area,

with access to an open terrace.

And this feature here is a stone-carved sculpture

to compliment the rather large fireplace,

situated right here.

[Narrator] But the construction of this site

was shrouded in secrecy.

[Nusbacher] The egalitarian communist state of Bulgaria

[Nusbacher] The egalitarian communist state of Bulgaria

is hiding away something for the privileged,

in a state where nobody was supposed to be privileged.

[man 1] The work was done in complete secrecy,

because the government didn't want anybody to know

about the hypocrisy

that coursed through every aspect of it.

[Narrator] After this complex was completed in 1977,

Zhivkov liked it so much,

Zhivkov liked it so much,

he decided that even Bulgaria's elite would not be given access.

This place was meant to be for the many,

but one man decided to keep it for himself.

[translator speaking] What I remember is that a few years

after the completion of this building,

it became apparent that no one is allowed to visit it.

[Narrator] For decades, Zhivkov kept Bankya Residence

as his unofficial private country house.

But his behavior was earning him many enemies.

Zhivkov himself wasn't a particularly nice character.

He was very quick to eliminate any potential threats.

[Nusbacher] Everyone in his country hated him.

If they'd had the chance, they'd have gotten rid of him.

[Narrator] Derelict structures at the edge of the compound

reveal Zhivkov's increasing paranoia.

reveal Zhivkov's increasing paranoia.

Zhivkov wanted to beef up the security for himself and the people around him.

And so, he set up extra accommodation for his secret police.

[translator speaking] This was designed as a service structure,

with various purposes, to accommodate security, transportation, and equipment.

[Narrator] Unbeknown, even to the architects,

Zhivkov added a secret tunnel that connected the buildings.

However, his real protection was insured,

thanks to his Soviet overlords.

But that was soon to change.

[Narrator] In the 1970s, in Bulgaria,

an elaborate, brutalist, country palace housed the dictator Todor Zhivkov.

His safety was insured by his close personal friendship

with Soviet leader, Leonid Brezhnev.

Addicted to tranquilizers and alcohol,

Brezhnev had serious health problems.

Brezhnev had serious health problems.

So in 1979, Zhivkov brought his protector here,

to Bankya Residence.

[Jerram] Zhivkov invited him to come to this sort of cleansing mountain retreat.

And he wanted to kind of curry favor

with his kind of Russian masters.

[Narrator] Inside the retreat,

Brezhnev wallowed in the luxury.

[translator speaking] I was here right after the completion of the project,

and even took some photographs.

[Narrator] The architect-designed pool took advantage

of all the region's healing properties.

[translator speaking] I remember that back then,

this was a very interesting feature,

this ceiling, with its curved shape and aluminum cladding.

Its shape was created to draw your eyes out to the park.

The idea was to have the surrounding nature flowing into the pool.

[Narrator] The pool itself was full of Bankya's famed healing mineral water.

[translator speaking] As far as I remember,

the water level was reaching

up to the very top of this element here.

In other words, where I am standing at the moment,

my head is on the same level as the Head of State.

[Narrator] But Zhivkov's paranoia was growing,

and his secret police were increasingly aggressive.

and his secret police were increasingly aggressive.

Even those beyond Bulgaria's borders were not safe.

In 1978, Georgi Markov, a BBC World Services correspondent

and a Bulgarian dissident, was murdered on Waterloo Bridge

by a Bulgarian assassin,

using an umbrella with a poisoned tip.

[Narrator] Back home, the death of his daughter

made Zhivkov retreat even further.

He took up almost permanent residence at the site,

He took up almost permanent residence at the site,

kind of removed himself away from that tragedy.

[Narrator] And by the 1980s,

the death of his ally, Leonid Brezhnev,

followed by the softening of communism,

meant Zhivkov's days were numbered.

He was finally ousted in a bloodless coup in 1989.

He was actually kicked out of the residence.

And then he was held up for trial for embezzling money.

[Narrator] Zhivkov was convicted,

confined to house arrest

and died in 1998.

Meanwhile, the life of his beloved Bankya Residence

had taken a bizarre turn.

[Selwood] A Japanese billionairess bought it,

to convert it into a golf club.

She re-painted the site pink, and lived there herself.

[Narrator] The billionairess died in 1999.

And after a brief spell as an upmarket brothel,

And after a brief spell as an upmarket brothel,

Bankya Residence was abandoned.

[Narrator] Iliyan Nikolov's father was never given credit

for his unique architectural work.

[translator speaking] This was, of course, done on purpose,

based on his political views.

[Narrator] Iliyan hopes to change this,

and reverse the fortunes of Bankya Residence.

[translator speaking] Let's find a way to revive this place.

[translator speaking] Let's find a way to revive this place.

Let's give it a second chance.

[Narrator] In Northern Germany,

on the banks of the River Weser

sits a mammoth building.

[Nusbacher] It's a vast expanse of cement,

that is just plunked down in the countryside.

that is just plunked down in the countryside.

It doesn't have any indications on the outside of what its function would be.

There's not really any windows,

there's only a couple of openings in the whole building.

[Narrator] Turns out, there's a cavernous interior.

This eerie structure hides clues in its construction.

[Nusbacher] The struts and the columns

that hold up this very heavy roof,

are clearly perfectly designed.

are clearly perfectly designed.

[Wawro] Massively manufactured from concrete and steel.

Clearly, it housed something very important.

[Narrator] Out of the gloom, a distinct order emerges.

[man 2] It's organized into a series of enormous bays,

with big, thick, concrete walls between them.

And as you work your way to the last couple of bays,

you can see that they've got water.

[Narrator] So who built these watery tombs,

and shrouded them in thick concrete,

and why?

[Narrator] This colossal and desolate structure

covers almost an acre of riverbank,

near the German town of Bremen.

Marcus Meyer is its scientific director.

[translator speaking] They started building here in the spring of 1943,

and the construction work continued for more than 22 months.

and the construction work continued for more than 22 months.

This bunker was designed to be bombproof,

to withstand the largest bombs available at the time.

They used state-of-the-art building techniques to build this.

We know from the age and from its overall military look,

that it was something built during World War II.

[Narrator] By 1943,

Germany was struggling to maintain its foothold in the Second World War.

[Meigs] The writing was really on the wall for the Nazis at this point.

It was only a matter of time before their Reich collapsed.

It was only a matter of time before their Reich collapsed.

[Nusbacher] Germany is being bombed from the British Isles,

from Italy,

and is being strangled by an economic blockade.

[Narrator] The precision building at this site

hints at how Germany planned to fight back.

[Meigs] The location might be a clue.

[Meigs] The location might be a clue.

It's right next to a major waterway

that flows into the North Sea.

What do you want to put here that needs access to the ocean?

[Narrator] With the Allies dominating the skies,

the Germans wanted to regain control of the Atlantic.

The most effective naval weapon that Germany has

is the U-boat, the German submarine.

[Meigs] They thought if they could build enough U-boats,

[Meigs] They thought if they could build enough U-boats,

to go out and sink as much allied shipping as possible,

then maybe they can negotiate some kinds of terms,

that would be advantageous to them.

[Wawro] The type 21 U-boat is what they had in mind.

This is going to be a diesel-electric submarine,

that can keep Germany in the war.

Can't just build it in a shipyard,

because the aerial bombing campaign is just pulverizing

all of the German manufacturing facilities.

So this place has got to be able to withstand a huge bombing raid.

So this place has got to be able to withstand a huge bombing raid.

[Narrator] The result is this.

The Germans' top secret U-boat manufacturing facility.

Codenamed Bunker Valentin, it's located far from the coast,

away from the Allies' prying eyes.

[translator speaking] Bunker Valentin was the largest project

undertaken by the German Navy

in the last two years of the war.

Yet, they thought they could keep the construction hidden from the Allies.

[Narrator] Secrecy was paramount.

And it was no mean feat

to keep the building of this enormous bunker under wraps.

[translator speaking] This was one of the most up-to-date

construction sites in Europe at the time.

It featured a mobile framework of concrete walls on wheels,

that could be moved around quickly.

[Narrator] The Nazi's greatest challenge

was how to build a bombproof roof.

They built large arches to hold up the roof.

They built large arches to hold up the roof.

Those are built on site, but then later lifted into place with cranes.

And then more concrete was poured on top of that.

By the time they were done, the roof was at least 15 feet thick.

[Narrator] But the Nazis knew this wouldn't be thick enough

to stand up to the Allies' bombs.

So they ordered some sections to be increased to 23 feet.

This vast piece of engineering came at a brutal cost.

This vast piece of engineering came at a brutal cost.

This building was essentially constructed with slave labor.

It's believed they used 10,000 to 12,000 prisoners

to work on this project.

[Narrator] It's not known how many sacrificed their lives

to bring this secret facility to near completion in less than two years.

[Meigs] This was conceived as

a really fast-paced assembly line for submarines.

a really fast-paced assembly line for submarines.

They'd essentially be bolted together in this facility.

[translator speaking] The submarine production was going to start here,

through that gate, where the individual segments of the sub

were to be brought into the bunker.

Then, where that water is,

they planned to align them on a large turntable,

before putting them on a system of wagons on rails.

[Narrator] The plan was that at each bay,

more of the submarine would be assembled,

more of the submarine would be assembled,

then passed along the system of rails.

[translator speaking] The idea was to put a wagon on rails here,

a wagon on rails there, and then connect them up.

Eventually, once all the individual segments

had been put together,

they intended to weld together the whole boat.

Ultimately, the completed submarine

had been pushed through the bunker on these rails,

three times lengthwise and four times crosswise.

[Narrator] In total, each submarine was intended to pass through 12 bays,

[Narrator] In total, each submarine was intended to pass through 12 bays,

until finally, it was ready to enter the lock chamber.

[translator speaking] This is the last station of a submarine assembly line.

The finished submarine would have come to a halt here.

Then this chamber would have been flooded,

and the boat would have dived, briefly,

to test whether the machines work under water,

to see if the seals would hold.

Then the boat would have continued out there to the river.

Then the boat would have continued out there to the river.

The plan was to let a fully equipped submarine

out into the River Weser, every 56 hours.

[Narrator] By 1945, the submarine assembly line

was on the brink of building its first state-of-the-art U-boat.

But unbeknown to German intelligence,

the British were watching.

[Narrator] Toward the end of the Second World War,

the German Navy was putting the finishing touches

on a secret submarine facility of epic proportions.

The Germans were convinced that the British had no idea what was going on.

But in fact, they were just biding their time.

[translator speaking] There's a British Secret Service file,

which documents this construction site in great detail,

basically, from day one.

So the Royal Air Force knew exactly what was going on here.

And they were particularly interested in how thick the roof was.

[Narrator] The British had no intention of attacking,

until the moment was right.

[Meigs] They let the Germans keep working on it,

keep pouring men and material and time and money

and effort into this huge project.

and effort into this huge project.

And the British knew the minute it was done,

they knew exactly what was going on.

[Narrator] March 27th, 1945,

20 Lancaster bombers of Britain's 617 Squadron,

aka the "Dambusters" head towards Bunker Valentin,

loaded with bombs.

They knew exactly how to target

the most vulnerable section of the bunker's roof.

[Wawro] They penetrate the thinner section, the West End,

and they get into the guts of the thing, blasting it apart.

[Narrator] Their timing was perfect.

[Meigs] The British did something very smart.

They could have bombed this project,

while it was being constructed,

but they didn't.

[Narrator] Though Bunker Valentin remained standing,

the damage was done.

Germany didn't have the time or resources to rebuild.

Germany didn't have the time or resources to rebuild.

And overnight, their hope of victory was gone.

And this enormous structure

didn't even start producing submarines.

[Narrator] After the war was over,

Bunker Valentin had one more onslaught to face.

In March of 1946, the British and Americans

decide that, "Hey, this Valentin Submarine Bunker.

"It's the perfect place to test bunker buster bombs".

"It's the perfect place to test bunker buster bombs".

They fly a number of missions,

dropping everything in their inventory.

And amazingly, this Valentin submarine bunker withstands

even this barrage of aerial bombs.

[Narrator] The colossal bunker

has been slowly crumbling ever since.

In Australia, in the middle of Sydney Harbor,

sits a tiny island.

sits a tiny island.

[man 5] It's cluttered with rusting cranes,

old industrial-looking warehouses,

and washed-up boats.

[Narrator] An incongruous villa stands alone.

And beyond, is an imposing structure.

[man 5] There are these big windows and airy rooms,

but there's something else.

There're bars on the windows, tiny cells inside.

There're bars on the windows, tiny cells inside.

Clearly, most of the people here were not here by choice.

[Narrator] The building is covered in spikes

and hand-carved scratches,

clues, as to who built the industrial structures

that crowd this place.

[man 6] There's what looks like a huge warehouse

with a turbine inside.

And there's a sign on it, and it reads Scotland.

And there's a sign on it, and it reads Scotland.

[Narrator] Below ground, there's more.

[man 5] An eerie tunnel runs for almost 200 yards,

right through the belly of the island.

Well, what was this built for?

[Narrator] Polly Nowicki has spent seven years

exploring this island, which was first inhabited

by Australia's indigenous Eora people.

by Australia's indigenous Eora people.

[Nowicki] They called this place Wareamah.

And it was a special, sacred place for women

to travel in canoes here,

and it was the place of childbirth, for privacy.

[Narrator] But when the British arrived in the 18th century,

they changed this place from a cradle of birth to something far more deadly.

And they gave it a new name.

[man 5] The name makes it sound like quite a chirpy, chipper place.

[man 5] The name makes it sound like quite a chirpy, chipper place.

However, it was anything but.

[Narrator] Renamed Cockatoo Island,

it was perfect for what the British had in mind.

[man 6] In 1788, the area that we now know as Sydney

was opened up as a penal colony for the British,

but it quickly became overcrowded.

And this is where Cockatoo Island

comes into the picture.

[Narrator] The first convicts to arrive here, in 1839,

faced a brutal task.

The convicts excavated tons of rock,

to construct their own prison buildings.

[Nowicki] Each convict was assigned a signature.

They would use a small chisel to carve out this shape.

You can see the X's, the lines,

and the different kind of shapes.

So, each signature meant that they were assigned

a different amount of bricks to build.

[Narrator] They built themselves a grizzly punishment block.

[Narrator] They built themselves a grizzly punishment block.

So this is solitary confinement,

where they would keep prisoners for up to 12 days.

[Narrator] The abandoned jail

reveals the appalling living conditions.

On the windows, you can see

that men have actually grabbed up

to try and get a breath of fresh air.

[Narrator] Only one prisoner ever managed to escape,

with the help of his wife, who was over on the mainland.

with the help of his wife, who was over on the mainland.

[Nowicki] She rides the horse there,

she climbs down the edge of the cliff,

and she swims to Cockatoo Island.

It's about a 20-minute swim.

There's bull sharks, strong currents,

all sorts of things in her way,

on top of her, supposedly, being pregnant.

[Narrator] She gives him what he needs to cut his shackles,

and he manages to swim to the other side, to freedom.

Once the prison's construction was completed,

the inmates were set to task

on an even more formidable challenge.

on an even more formidable challenge.

One that would only further the might of their oppressors.

[Narrator] By the mid-19th century,

Cockatoo Island in Sydney Harbor had become a notorious prison.

But thanks to its location,

the British had other plans for it.

European nations became much more interested

in expanding their empires in Southeast Asia and the Pacific.

Britain needed a place in this part of the world,

Britain needed a place in this part of the world,

where they could repair and maintain ships.

It was decided that Cockatoo Island,

with its deep water and abundant supply of convict labor,

would be the ideal location.

[Narrator] They started work on a dockyard in 1847.

This is Fitzroy Dock.

It was constructed by convict labor,

and they had to carve it away with a small kind of pitch hammer.

and they had to carve it away with a small kind of pitch hammer.

An estimated 1.5 million cubic feet of rock was excavated.

And it was only supposed to take 470 days.

But it ended up taking years,

due to the unruliness and unrest

of the poorly treated convict workforce.

By September 30th, 1857,

the dock was finally ready to use.

[Nowicki] Without water, it's about four meters deep.

[Nowicki] Without water, it's about four meters deep.

It's not as deep as it looks,

but it is quite wide and quite long.

[Narrator] But there was a problem.

There was no power on Cockatoo Island,

and nowhere to build a generator.

To transform the basic stone dock

into a modern naval powerhouse,

Chief Engineer Gother Kerr Mann

was forced to take drastic measures.

Marks on a sandstone cliff face reveal what happened next.

Marks on a sandstone cliff face reveal what happened next.

There's these lines of sort of dynamite ridges,

where he's dropped that dynamite down,

and he blew up that side of the island,

and he was changing the shape of the island

to make way for this huge turbine hall.

[Narrator] In one of the biggest structures on Cockatoo Island,

cutting edge technology gave Fitzroy Dock

the capacity to build and repair modern warships.

Inside the turbine hall, this is one of our iron giants.

It came from Scotland in parts,

and it is, actually, a huge scale lathe,

and it's used for sort of carving out metal.

[Narrator] And to enhance the scope of their prized facility,

the British commissioned another, even bigger dock.

[Auerbach] Naval technology doesn't stand still.

And as sail ships gave way to steam ships,

the dock had to be changed

the dock had to be changed

to accommodate these newer, larger vessels.

[Narrator] So, now, the convicts had to carve out this,

Sutherland dock.

It was the biggest single dry dock in the world.

The addition of a tunnel to move workers and machinery underground,

made Cockatoo Island the leading naval facility in the South Pacific.

[Gutierrez-Romine] This place ended up being a vital part

of Australia's response to war.

of Australia's response to war.

[Narrator] Throughout the first half of the 20th century,

it was put to the test.

After docking nearly 2,000 ships during the First World War,

Cockatoo Island would play a vital role in the next one.

After Japan entered World War II in 1941,

the stage was set for naval warfare in the Pacific.

[Narrator] And when the American warship, USS New Orleans

was bombed by the Japanese in 1942,

she retreated to Cockatoo Island.

Although the dockyards were able to make the ship fighting fit again,

the real damage had been done.

This is where it came.

So in 1942, they would dock side here,

up to 60 lead-lined coffins, to send back to America.

up to 60 lead-lined coffins, to send back to America.

[Narrator] After the war,

shipbuilding and repair declined.

The last ship to be constructed on the island

was HMAS Success, which launched in 1984.

It was the largest naval vessel

ever to be built in Australia.

[Narrator] Finally, in 1991,

the Cockatoo Island dockyards closed down.

Today, this trove of maritime industry

Today, this trove of maritime industry

needs preserving.

[Nowicki] We're constantly working on trying to rehabilitate

all the old machines on the island.

That's interesting, innovative, and fascinating.