Original subtitles

[narrator] A cosmic wreck that seemed to have made contact.

It really looked like the signal was coming from

a faraway planet.

[narrator] Clandestine ruins that decided a nation's fate.

A lot of what went on here was top secret, for good reason.

[narrator] And a fantastical old castle built on a deception.

[narrator] And a fantastical old castle built on a deception.

I see a lot of storybook.

There's a lot more to this place than meets the eye.

[narrator] Decaying relics,

ruins of lost worlds,

sights haunted by the past,

their secrets waiting to be revealed.

In Georgia's Piedmont region,

two lonely structures gaze at the heavens.

You've got all these trees.

And then all of a sudden, it breaks through

and you see something that you completely don't expect to see here.

There's no mystery as to what these are.

They're two great, big satellite dishes.

They're two great, big satellite dishes.

They've clearly been sitting there in the weather

and not being used for some time.

[narrator] Built at great expense,

what is unclear is the exact purpose of this facility.

[Jaega] Cold, white walls, no windows, air vents,

these two great, big dishes on top,

surrounded by fencing.

It's like some sort of villain's lair.

[Jim Meigs] When you get inside, you can see that it'd been stripped pretty bare.

Any valuable equipment was taken away long ago.

Any valuable equipment was taken away long ago.

Now, it's just kind of a hodgepodge of junk.

There's stacks of wooden chairs,

there's even an old refrigerator.

[narrator] Once occupied by brilliant scientists,

this complex was engaged in the search for something extraordinary,

beyond planet Earth.

There was a moment when we thought we had proof that something was out there.

And this complex was at the center of that story.

When these structures were built in 1976,

it was called the Woodbury Earth Station.

It was built by AT&T, the giant telecoms company.

[Jim] In the 1970s, the telephone industry was going through a revolution.

It was becoming feasible to

send all kinds of data, including telephone calls,

up to satellites in orbit.

So, AT&T built these two dishes to serve as an uplink and downlink

for this satellite phone transmission system.

for this satellite phone transmission system.

[narrator] The unique landscape here made it perfect for the Earth station.

Scott Harris is a planetary geologist,

who has investigated its extraterrestrial origins.

[Scott] Well, we're in this unique depression, called the Cove.

My colleagues and I have been researching the site for about 20 years,

looking at the possibility that these radio telescopes

actually sit in the middle of an ancient impact structure.

[Jim] This cove dome crater appears to be the remnant

[Jim] This cove dome crater appears to be the remnant

of a large meteor strike.

Whatever hit this, hit it hard enough

to pulverize rock, even melt the rock,

and then leave that crater ring around the side.

[Scott] There's no coincidence that these dishes are in the middle of that crater

because the deep depression, about 300 feet deep,

provides a radio and microwave free zone.

[Jim] You can build your big dishes here,

and they'd have very little interference

and they'd have very little interference

from surrounding electromagnetic sources.

[narrator] But Woodbury Earth Station's service would be short lived.

The thing about satellite technology is it changes so rapidly.

So by 1980, just a few years after they'd built it,

AT&T retired this facility and abandoned it.

But that was not the end of the story here, far from it.

Soon, these giant dishes would be involved in a close call.

Something truly out of this world.

Something truly out of this world.

[narrator] Paul Steffes is a former NASA scientist

and was on the ground when the Woodbury site

was at the center of this "close call."

[Paul] Our team leader always kept a bottle of champagne in her refrigerator.

After this detection was made,

they made sure the bottle was still there and full.

[narrator] In 1996, Paul wasn't working for NASA,

but an independent organization known as SETI.

[Katherine] This was an organization that originally had been funded by

[Katherine] This was an organization that originally had been funded by

the American Federal Government.

Their funding gets cut and they become a non-profit.

Their mission is to find evidence of extraterrestrial intelligence

by searching space for signs that something is out there.

[narrator] And Woodbury would play a key role in their latest search,

Project Phoenix.

[Paul] We operated as part of the Project Phoenix of the SETI institute

from 1996, all the way through the year 2000.

Project Phoenix was a successor to our NASA program

Project Phoenix was a successor to our NASA program

of searching the skies for artificial signals

emanated by foreign, or rather, distant civilizations.

[Jim] Why would you wanna use a radio telescope to look for intelligent life?

Well, the theory is,

that if some intelligent civilization developed anything like humans did,

at some stage, they might invent something like radio,

or something like television,

beaming signals around their planet.

So, that's what they started looking for.

So, that's what they started looking for.

[narrator] SETI had big plans for the Woodbury Earth Station

But it had not been built to scour the heavens for signs of life.

The requirement for the SETI program

to be able to point precisely at given targets,

was far in excess of the previous pointing capability of this facility.

In 1996, SETI provided a million dollars to upgrade one of the dishes

so it could become part of Project Phoenix.

[Katherine] They put in a new motor,

[Katherine] They put in a new motor,

they took out an old stairway,

and they put in a new flexible cable carrier,

called the "Twister."

[Paul] The horn that we installed on the center

of the southern dish on this facility,

was built so that we could monitor signals over a wide range of frequencies.

[narrator] When the upgrades were complete,

it was renamed the Woodbury Research Facility.

It would provide follow up detection for another SETI station

in Green Bank, West Virginia.

in Green Bank, West Virginia.

So, having this device, which we called a "FUDD," Follow Up Detection Device,

was the key for being able to quickly scan the skies

and excise any radio frequency interference.

If you watch the movie, Contact, after their detection of a signal,

Jodie Foster kisses the screen and says, "Thank you, Elmer."

And of course, the software that ran the FUDD was named Elmer.

[narrator] Woodbury was essential to making sure that

[narrator] Woodbury was essential to making sure that

any signals from one facility,

could be immediately verified by the other.

They were there to double check.

To confirm signals identified as alien.

[narrator] Less than a year later, SETI made contact.

[Jim] Woodbury's sister facility got a signal

that looked really distinctive.

This might be the greatest scientific breakthrough in human history.

This might be the greatest scientific breakthrough in human history.

[narrator] In 1997,

scientists from the Search for Extraterrestrial Intelligence,

or SETI,

were using the Woodbury Research Facility

to support their search for alien civilizations.

At 6:00 a.m., on June 23rd,

they made contact.

They were scanning a star named "YZ Ceti"

They were scanning a star named "YZ Ceti"

about 12 light years away from our sun,

when they started to hear something that they thought might be promising.

So, this really looked like it might be the big one.

[Jaega] Being in that room, in that moment,

you'd go crazy with excitement.

[narrator] They needed to use Woodbury to check that the signal was genuine.

But disaster had struck.

It was offline.

About a week and a half before the close call,

About a week and a half before the close call,

a lightning storm struck the dish

and caused damage to one of the receivers that was used to monitor

for Project Phoenix.

So, as a result, we were unable to run the Follow Up Detection Device those days.

So, the dish was down.

It wasn't available to confirm this possible sighting

of an alien intelligence.

The researchers were biting their nails,

they were trying to figure out how they could confirm it.

[narrator] While Paul's colleagues were prepping the champagne glasses,

[narrator] While Paul's colleagues were prepping the champagne glasses,

he had to catch a flight to SETI headquarters in California.

This gave him some time to think.

As I was flying on the plane, I had with me

a paper copy of all of the space craft

that we had in our database.

And the more I looked, the more I realized that

this specific frequency

corresponded to one that had been assigned to a satellite called SOHO.

SOHO was a deep space explorer designed to monitor the sun.

SOHO was a deep space explorer designed to monitor the sun.

[narrator] The SETI telescopes were pointed into deep space.

And on its orbit around the sun,

the SOHO satellite had crossed their path.

[Jaega] The signal was being made by intelligent life.

Unfortunately, it was us.

[Katherine] Of course, if Woodbury had been online at that moment in time,

this would all very quickly have been squashed.

But they weren't there at the moment that they were needed.

[narrator] SETI continued to operate the Woodbury Research Facility until 2000,

when technological innovations outpaced this site once again.

It has remained dormant ever since,

silently watching the skies.

Today, although SETI has left Woodbury behind,

they remain committed to searching the universe for intelligent life.

After all these years, SETI is still at it.

After all these years, SETI is still at it.

They have a new project called Breakthrough Listen,

where they are continuing to search for any kind of sign

that we're not alone, that there's someone else out there.

The legacy of Woodbury is that

it shows if we don't look for this extraterrestrial intelligence,

we'll never find it.

I think we should cast our eyes to the heavens

and keep on searching.

You know what? I do think the truth is out there.

[narrator] In the Indian state of Rajasthan,

is an engineering marvel that protected an empire.

[Rob] There are mountains all around.

And then, dominating this landscape,

is this huge majestic structure.

[Geoff] Looks almost like the Great Wall of China.

But we're definitely not looking at that 'cause we're not in China.

But we're definitely not looking at that 'cause we're not in China.

[Lynette] And as we get closer,

we get a feeling, not only for how massive these walls are,

but we get a feeling for what a huge amount of ground they cover.

[narrator] Commanding gates guard the treasures held within.

There are buildings full of beautifully carved statues

and tall pillars supporting vaulted roofs.

And there's really a distinctly religious feel to the place

because many of these interior structures look like temples.

because many of these interior structures look like temples.

All of this massive imposition

of human will on the wilderness,

is part of the vision of one man.

And its history tells a story of faith,

conquest and betrayal.

[narrator] Sandeep Sharma is a local historian fascinated by this site's past.

Today, it is bereft of life.

When first occupied, it was a hive of activity.

[narrator] This is the Kumbhalgarh Hill fort.

[narrator] This is the Kumbhalgarh Hill fort.

This place was built by Rana Kumbha,

who was the ruler of Mewar, one of the great kingdoms

in Rajasthan, in India.

Mewar was a part of a far more fragmented India than we know today.

This was a time of conquest and conflict.

All of the ruling families were constantly fighting over land.

The threat of an invading army was very real.

[narrator] With the kingdom's capital over 50 miles east in Chittaurgarh,

[narrator] With the kingdom's capital over 50 miles east in Chittaurgarh,

this fortress was a second line of defense.

[Lynette] If Mewar is attacked,

Rana Kumbha wants to take the capital,

the administration, the civil service,

everything required to run his kingdom,

and tuck it safely behind walls in the mountains.

[narrator] Kumbhalgarh was the crown jewel in the Mewar kingdom's defenses.

But the first blood spilled here was before construction even began.

But the first blood spilled here was before construction even began.

[Sandeep speaking]

Locals, still to this day, say that

when they started building it, each time they placed a stone,

or built part of a wall,

that evening the whole thing would crumble back down to the ground again.

[Rob] King consulted one of his spiritual advisers

[Rob] King consulted one of his spiritual advisers

who said that the fort couldn't be built

until somebody voluntarily gave their life as a sacrifice.

So they say that a wandering pilgrim,

or perhaps one of the King's troops,

came forward, volunteered to be the sacrificial lamb, so to speak.

As the story goes, he began walking up a hill.

And as he climbed, he was beheaded.

His head, struck off by a sword,

rolled to a stop where one temple was built

rolled to a stop where one temple was built

in his memory.

[narrator] Once the curse had lifted,

construction began in around 1443

and took 15 years to complete.

[Sandeep speaking]

[Geoff] And it's really just staggering, the scale of this place.

[Geoff] And it's really just staggering, the scale of this place.

We're talking seven massive gates.

Seven massive bastions.

When finished, it proved to be one of the most impenetrable fortresses known to man.

The heavily fortified battlement stretched for 22 miles,

completely surrounding the fort and the settlement within.

[narrator] But this impregnable bastion

could not protect the pious King from an internal enemy.

[narrator] Brutally murdered, this would be the first of two great betrayals

that would see Rana Kumbha's impregnable fortress fall.

[narrator] The sprawling Indian fortress of Kumbhalgarh

was built to protect the Mewar kingdom from invasion.

But despite its formidable defenses,

its devout ruler Rana Kumbha would soon meet a grisly end.

Inside its walls.

[narrator] The murderous heir, Uday Singh,

was driven by ruthless ambition.

But he didn't get to rule for long.

Uday Singh wanted the power, wanted the prestige.

He then set out on the road and was struck by lightning.

He then set out on the road and was struck by lightning.

[Rob] Many believe that his untimely death

was a divine punishment for his betrayal.

[narrator] After his father's murder,

and Uday's dramatic demise,

the fort lost its importance to the rulers of Mewar.

Until a great, new ruler decided to resurrect it

in the late 1500s.

[Rob] The new King's arch enemy was Akbar the Great,

the leader of the Mughal empire.

Pratap spent his entire life fighting the Mughal empire.

And its armies tried, on many occasions, to capture the fortress.

But every time, they were unsuccessful.

[narrator] Kumbhalgarh remained impervious to direct assault.

It would take yet another act of treachery to finally breach it.

It would take yet another act of treachery to finally breach it.

Some say a traitor inside the fort poisoned the water supply.

[Lynette] And that meant that with the walls abandoned,

and the gates abandoned,

Akbar and his Mughal army were able to come in and take over the city.

[narrator] According to legend,

Pratap eventually managed to take back what was rightfully his.

Pratap eventually managed to take back what was rightfully his.

But after his death in 1597,

Kumbhalgarh's significance went into a long decline.

Following India's independence from the British,

the fort stopped being used as a residence by rulers in the region.

And it's been empty ever since.

[narrator] In 1951,

Kumbhalgarh became a protected monument.

Kumbhalgarh became a protected monument.

Today, its gates are open to all

who want to witness its grandeur.

This is really one of the more spectacular sites in the world.

And it gives us a really fascinating insight

into the glories of Indian civilization.

And into the ferocity of competition

between these warring Indian city states.

[narrator] In the quiet countryside, north of London,

lie remnants of Britain's incendiary past.

The urban sprawl ends and suddenly, there's this vast expanse of countryside.

It looks like most of this area is surrounded by fences with barbed wire

on the top.

[man] It was patrolled 24-hours a day, seven days a week,

by armed security guards

because of the materials they were dealing with.

And some of the secret work that went on to this site.

[narrator] Scattered across a vast area,

are traces of a vital and deadly industry.

[Jim] Some look like they could be hundreds of years old.

Others look like they're from

a more recent industrial era.

[Jaega] Smashed windows, peeling paint, cracked concrete,

[Jaega] Smashed windows, peeling paint, cracked concrete,

birds nesting in the rafters.

It's quite an eerie place to be.

You can't help but be drawn by this unusual curved tunnel,

which leads into a circular room, inside the hill.

[narrator] Propelled by a moment of incredible scientific advancement,

these overgrown structures would play a key role

in unleashing violence on a scale never seen before.

[narrator] In the quiet countryside, north of London,

lies a site that is still shrouded in secrecy.

As you go past the "No Entry" sign, into this dark tunnel,

you find yourself in a concrete bunker

with a strange fortified room in its center.

[Dominic] You can tell it is relatively modern.

But that really is all you can tell.

[Laurence] Very little is known.

[Laurence] Very little is known.

Probably all still covered by the Official Secrets Act.

[narrator] Laurence Burnett is a local expert who has spent 20 years

uncovering the history of this site.

[Laurence] They provide a very strong chamber that can withstand

enormous pressures, enormous stresses.

Um, and that's really the only...

evidence we've got of, um,

what was going on in this part of the site.

[Jim] It's possible we'll never know all the details.

A lot of what went on here was top secret for good reason.

[narrator] But a ruined building nearby suggests that this place

is part of a much longer story.

[Laurence] This collection of buildings and structures is known as press house number 2.

On the left hand side, we got the press.

A metal structure.

Directly behind me, you got the big blast wall.

And on the right hand side, you got the hydraulic house,

And on the right hand side, you got the hydraulic house,

which generated hydraulic power

to actually work the base of the press.

This place was definitely producing something dangerous.

Why else would they put a big, thick wall between the waterwheel

and the metal machine?

This whole thing was set up, um,

as a process, one of the 17 steps to make gunpowder.

[narrator] Spread over an area of 170 acres,

this is the Royal Gunpowder Mills, Waltham Abbey.

this is the Royal Gunpowder Mills, Waltham Abbey.

Originally, a private enterprise,

it is rumored to have supplied gunpowder

to some rather infamous clients.

It's even possible that the gunpowder that Guy Fawkes, famously,

tried to use to blow up Parliament,

might've been manufactured here.

[narrator] But its biggest client by far,

was the British government.

So much so, that they bought it in 1787.

[Jim] They took it over and said,

"This is too important to be left to some private owner.

"This is too important to be left to some private owner.

We need to run this as a national defense priority."

[Dominic] It developed over centuries to become one of the most important

centers of gunpowder production in Britain.

Trafalgar, Waterloo, the Crimea,

the Boer war, the American war of independence,

the first Indian war in independence and countless other battles.

The gunpowder made here helped fuel the unstoppable British military machine.

[narrator] But as scientists were making explosive new breakthroughs

[narrator] But as scientists were making explosive new breakthroughs

in the mid-1800s,

Europe was teetering on the edge of Armageddon.

[Dominic] The discovery of new chemical compounds,

and new processes to manufacture them,

resulted in an arms race,

that was to lead to industrialized chemical warfare.

[narrator] Dubbed, "The Chemist's war,"

this conflict would see the deployment of new and evermore deadly weapons.

this conflict would see the deployment of new and evermore deadly weapons.

A ruin, hidden in the undergrowth shows how Britain was working to

keep ahead of its competition.

The material that was produced on this site was a liquid.

And it's so sensitive, so volatile,

that the only way you could produce it

was at the top of a manmade hill.

And this is what this structure is here.

[Jim] This was a new type of explosive.

It was far more powerful

and made a faster, moving explosion than gunpowder.

[Laurence] This building is the nitrator.

[Laurence] This building is the nitrator.

And this was solely built to produce nitroglycerine.

[narrator] The inner structure which has rotted away,

was where the nitroglycerine was produced.

And all that remains today,

is proof of just how volatile this new chemical was.

Nitroglycerine is made by the combining of two acids.

Nitric acid and sulfuric acid with glycerin.

It's very dangerous work.

And it's only stable between 60-70 degrees Fahrenheit.

And it's only stable between 60-70 degrees Fahrenheit.

[Laurence] This is actually a big blast vault.

So, if there anything does go wrong,

the energy from the blast,

would go out through the curved exit way,

go straight up in the air.

Fortunately, it never happened here.

Um, otherwise this building probably wouldn't still be here.

[Dominic] The highly explosive qualities of nitroglycerine

made it absolutely ideal for the purpose.

But the problem was its extreme volatility.

And it couldn't be transported in its pure form, to the frontlines.

And it couldn't be transported in its pure form, to the frontlines.

[narrator] The raw nitroglycerine needed to be combined

with other compounds to stabilize it.

This led to the development of a revolutionary new product in 1889.

Cordite.

[Laurence] Cordite, as a propellant, was absolutely fantastic

compared with the previous propellants that were used.

Um, it's smokeless,

there was more energy per given mass.

And it was used from,

And it was used from,

uh, anything from pistols, rifles,

large cannons, naval guns.

It was just a revolutionary product.

[narrator] When the first World War erupted in 1914,

the demand for cordite would skyrocket,

pushing the Royal Gunpowder Mills to breaking point.

[narrator] In 1914, the Royal Gunpowder Mills, north of London,

was racing to supply the frontlines

with a revolutionary explosive called cordite.

The British Expeditionary Force, in 1914,

was modern, agile and mobile.

But when it arrived on the continent,

they were expecting one kind of warfare,

and it soon turned into something very different.

and it soon turned into something very different.

[Jim] People could be manning artillery guns miles from the front,

raining death down on an enemy they had never seen,

out of the sky. Both sides did this relentlessly.

Month after month, year after year.

[Laurence] If Waltham Abbey wasn't producing cordite,

then we would've been in serious trouble.

At the time, there was no other factory that could produce that amount of

high quality propellant.

high quality propellant.

[narrator] But as the scale of the war became all encompassing,

to keep Britain in the fight,

cordite production had to be ramped up.

And fast.

[Laurence] You had belt driven equipment,

belt driven presses which made a hell of a noise.

You have the clattering of the machinery, the pumps,

um, the belt slapping about.

At the height of production, the factory was producing

75 tons of cordite every week.

75 tons of cordite every week.

[narrator] But it soon became clear that there was a problem.

They were short-staffed.

[Jaega] With all the men away fighting in the war, and the demand for cordite

like never before,

they hired over 3000 new employees to help produce it.

And most of them were women.

[Laurence] They kept the place going, really.

Bit of initial training,

and they got on with it. It was maintenance,

production, transport,

production, transport,

absolutely everything on site

to keep the site going.

That is... absolutely amazing, really.

[narrator] As the war progressed,

even the scaled up facilities here couldn't keep up.

The government built new, larger factories around the country to meet demand.

But it was the Royal Gunpowder Mills that pioneered the production of cordite

at a moment when all might've been lost.

[Laurence] The legacy to the country is that it saved our bacon, really.

It was vital, absolutely vital to the success

of the, you know, our forces.

Incredible. [chuckles]

[narrator] The complex closed down in 1945.

But as the mysterious bunker at the heart of the complex suggests,

it would still play a vital role in protecting Britain for years to come.

it would still play a vital role in protecting Britain for years to come.

[Jaega] Just three days after the mills were shut down,

it was reopened again.

It was turned into a place for weapons research and for experimentation.

[narrator] The Cold War facility was finally decommissioned in 1991,

ending over 300 years of cutting-edge research at Waltham Abbey.

[Jaega] But lots of what went on here is still classified.

Still, to this day, we don't really know

Still, to this day, we don't really know

to the true extent, what happened here.

I mean, maybe we'll never know.

[narrator] In France's Loire Valley,

a fairy tale castle dominates the landscape.

When I look at this place, I see a lot of Disney.

It's sophisticated, symmetrical.

It's sophisticated, symmetrical.

Just gorgeous.

It's got these beautiful porticos, balustrades, terraces.

All done in renaissance style.

[narrator] Surrounded by a deep moat,

it was clearly built to be defended.

But that's not the only excavation that's taken place here.

[Claire] If we move further in,

that's when it starts to get interesting.

[Lynette] There is an entrance down there

that shows that there is a great deal going on beneath the surface.

that shows that there is a great deal going on beneath the surface.

[In French] We are now heading to a part of the castle which is much more mysterious,

as it remained closed off until the beginning of the 2000s.

[Lynette] It's cool, it's damp and it's dark.

There are places where, as you walk, you realize

you're walking down a ramp.

And that you're no longer walking on a corridor,

And that you're no longer walking on a corridor,

you're not walking on a steady floor,

the floor is dropping away beneath you.

We're talking hundreds and hundreds of meters,

the corridors and little alleyways,

and all sorts of different tiny rooms and caverns and spaces.

[Lynette] This is a place that was dug out with hand tools.

We can almost, when we look at these marks,

imagine the sweat

of good, French stone cutters

of good, French stone cutters

digging their way into this hilltop.

[narrator] Herve Chaudron has spent 10 years uncovering this hidden world

below Chateau de Breze.

[Herve] Currently, we find ourself in Breze's foundations.

In other words, the underground castle.

This castle was built manually during the 9th century.

[narrator] This was a place of last resort.

Built out of the fear of a rampaging band of warriors,

advancing up the nearby river Loire.

advancing up the nearby river Loire.

[Lynette] This is a river that leads right into the Atlantic Ocean.

It was a highway for peaceful trade

and it was a highway for moving goods to market.

And it was a highway for the Vikings.

[narrator] In the 9th century,

Viking raids across France grew in their frequency and ferocity.

Including an event in 885 AD

that would shock the entire country.

that would shock the entire country.

The siege of Paris.

That siege went on for nearly a year.

It was absolutely brutal and vicious.

The Vikings took no quarter.

They slaughtered people, they enslaved people.

They took whatever wasn't nailed down.

[narrator] These cutthroat warriors might soon turn their attention

to Chateau de Breze.

[Lynette] And when the Norse people went Viking,

they were coming for plunder.

they were coming for plunder.

[narrator] In the 9th century,

Viking raiders were marauding through France.

And the lords of Chateau de Breze

turned to the ground beneath their feet for protection.

If you were a big landowner in France at the time,

you had to take countermeasures.

You had to prepare to defend yourself against the Vikings,

or hide from them.

or hide from them.

[narrator] Their survival would rely on a deception.

Convince the Vikings there was only one castle. Not two.

So, secrecy was its first defense.

And the Chateau de Breze is unique in that,

they decided, "Okay, we're gonna have a relatively modest palace above ground.

You would abandon the structure above.

You would let the Vikings take it, loot it, have their way with it,

and you would vanish into this secret underground labyrinth.

[narrator] It wasn't only people's lives at risk,

[narrator] It wasn't only people's lives at risk,

but their livelihoods.

This was an ancient survivalist bunker.

[Claire] They didn't keep money in banks.

Wealth wasn't in something, you know, that was hidden away.

It was literally within the food and the chattels

that you had in your location.

That's all you had. That's all the wealth you had.

And that had to be protected at any cost.

These stables were carefully designed for animals living underground.

This is why we have a trough,

which was used to distribute hay and water.

[narrator] With these extensive preparations,

its inhabitants could survive down here for some time.

How long exactly, unfortunately, we do not know.

But we think around 15 people could survive underground for a few months.

[narrator] If the raiders above somehow discovered the hidden entrances

[narrator] If the raiders above somehow discovered the hidden entrances

to this subterranean refuge,

it was designed to be defended to the very last.

The only access is through a narrow ramp, or narrow stairs,

so where people could come down, at most, two abreast,

so troops at the bottom could hack them up as they tried

to come down in relatively small numbers.

To protect the entire site,

holes were drilled into the walls in order to have a clear shot of this corridor.

A single archer, a determined fighter,

could defend the entire underground system.

[narrator] It's not known whether these defenses were ever discovered

or put to use.

And eventually, the threat of Viking raids passed.

But that was just the start of the fortifications here.

There was still a threat of civil war in France between

candidates for the French throne,

which this family might become involved

and might need a defensive position.

and might need a defensive position.

But also, I imagine there were all sorts of pandemic diseases

circulating around France, Europe and the world at the time.

[narrator] Beginning in the 15th century,

and taking more than 200 years to complete,

the deep moat was dug,

and the new owners used the excavated stone

to build a more imposing castle above.

They really fixed it up, they expanded,

they built it out in classic renaissance style.

[narrator] Faced with the prospect of deadly diseases,

[narrator] Faced with the prospect of deadly diseases,

and the development of new, more destructive weaponry,

the Lords of Breze, again,

turned to the ground beneath their feet.

The main threat to a castle is cannon.

Great, big gunpowder cannon

smashing the walls to pieces.

And if all of the working parts of your castle

are below ground level,

where the cannon can't get them,

where the cannon can't get them,

then it doesn't matter what the enemy does

to the top half, to the part above ground.

[narrator] Matching the opulence of the new construction above ground,

the stronghold below was also overhauled.

[Geoff] You had a relatively crude refuge

created in the medieval period against the Vikings,

that was now expanded into a much more expansive tunnel network.

[narrator] But these new tunnels came with a few important upgrades

[narrator] But these new tunnels came with a few important upgrades

to deal with the latest military technologies.

Right now, we're at the very end of the long underground passageway.

Its purpose was to connect the overhead castle to the bottom of the moat.

Thanks to these two firing posts,

it was possible to protect the entire corridor

and shoot attackers through the grate.

[narrator] Using the same principles as the earliest tunnels,

the new construction would allow the defenders

the new construction would allow the defenders

to hold out against even the most well-armed intruders.

People are going to be blazing away at you with muskets

and handguns, and arrows and boiling oil.

And all of this place is going to be a deathtrap

for anybody who tries to get in.

You have sort of fake tunnels installed to deceive

invaders who would go down the wrong tunnel, become trapped in a dead end

and be overwhelmed.

[narrator] Despite its formidable defensive capabilities,

[narrator] Despite its formidable defensive capabilities,

Chateau de Breze was never put to the test.

If your fortress is good enough,

if everybody knows that even if they destroy the towers,

the fortress will keep on fighting from below,

nobody's going to attack.

And you know what? It worked.

This fortress was well enough built

that nobody ever even tried to get in.

that nobody ever even tried to get in.

But had anybody ever tested it,

they would've had a very bad, bloody nose.

[narrator] Kept as a close secret over the following centuries,

the underground stronghold faded into obscurity.

This site was hidden for many centuries because, aside from the local lord and his family,

nobody else had access to the hideout.

It only recently reopened to the public in 2000.

It only recently reopened to the public in 2000.

[narrator] Today, Chateau de Breze's dank tunnels

have found a very fitting new purpose.

These cool, dark caverns are perfect for storing wine

that's still made here on the estate today.