Original subtitles

*

Narrator: a ruined compound On the edge of a peninsula,

Home to a famous outlaw...

It clearly took a huge amount Of money to build this place,

So why did they leave? What happened here?

Why is it so badly damaged?

Narrator: ...Alien-looking structures With no apparent purpose...

They sit isolated and marooned

On this piece Of abandoned marshland,

And they feel other-worldly.

And they feel other-worldly.

A

Narrator: ...And cottages Concealing an explosive secret.

Underneath these charming Destroyed houses

Is clearly something A bit sinister.

*

Narrator: engineering Marvels now abandoned...

Ruins shrouded in mystery.

Within these decaying structures Are the echoes of history.

Within these decaying structures Are the echoes of history.

They speak of death And destruction,

But also human ingenuity And endeavor.

Each haunted shell ready To be unmasked

And tell its own unique story.

-- captions by vitac -- Www.Vitac.Com

Captions paid for by Discovery communications

In the rolling hills of guatape In colombia,

Beside a shimmering Turquoise lake,

Is a battered ruin that looks Altogether out of place.

*

Meigs: on the shores Of this enormous lake

Stands the ruins of something.

It's not really clear what.

Bell: it looks forgotten,

And in places, It's badly damaged,

Yet it clearly bears the Hallmarks of a luxury resort.

Interpreter: many people Who come and visit this mansion

Feel all sorts Of strange things.

Narrator: A collection of buildings

In various states of disrepair

Sprawl across 20 acres

Of this dramatic peninsula.

Throughout the entire complex,

There's a funny Combination of things --

Towers that look like They might be guard towers

Or maybe it's An ornamental feature.

It looks a little bit Like a cross

Between a playboy mansion And some kind of military fort.

Between a playboy mansion And some kind of military fort.

Bell: vegetation consumes Much of the structure now,

Growing through the roof And the crumbling facade.

Meigs: as you get closer, You can see some odd details.

The walls are very thick Or hollow in some places.

There's signs of some kind Of enormous explosion.

So this place clearly Has a story to tell.

Narrator: who lived here?

What caused this destruction?

And why did this become

And why did this become

One of the most Dangerous places on earth?

In 1983, hundreds of laborers,

Each with a specific job,

Got to work On this idyllic complex.

No expense was spared.

It had a swimming pool, Tennis courts, a football pitch.

None of which sound out Of the ordinary,

But that football pitch Doubled up as a helipad.

And it also had its own Private seaplane dock.

This place was anything But ordinary.

This place was anything But ordinary.

Narrator: william jiménez is A local resident

And was employed here As a security guard.

*

It took almost seven years To build the structures

That you can see here today.

Narrator: through these long Years of construction,

The surrounding area Went through a period

Of extraordinary transformation And not for the better.

Just 25 miles away Is the town of medellin.

Just 25 miles away Is the town of medellin.

*

By the mid-1980s,

It was referred to as the murder Capital of the world.

It was home to the infamous Medellin cartel,

Which at its height,

Was amassing up to $60 million A day in drug profits,

And its founding father Was pablo escobar.

When you're pablo escobar, You can never really relax.

He was always surrounded By security.

He was always surrounded By security.

He had armed guards.

He had walls that were built Like the walls of a fortress.

Escobar Wanted to be ready for anything.

Narrator: needing a safe retreat For his family,

Escobar built this -- Hacienda la manuela.

Named after his own daughter,

It was his family who would Primarily enjoy this complex.

Interpreter: his family used to Stay here occasionally.

His mother, his wife, And his children.

His mother, his wife, And his children.

It was an ordinary thing.

It was not a hiding place.

Narrator: this was one of A string of palatial properties

Enjoyed by escobar's family.

One nearby included A bullfighting arena and a zoo.

Hacienda la manuela, Though less extravagant,

Had secret compartments, Cavities,

And a maze of corridors

To go with the helicopters And speedboats

Ready to provide a rapid getaway Across the surrounding waters.

Ready to provide a rapid getaway Across the surrounding waters.

For all its luxury,

Security was always a priority.

Pablo escobar had this Family retreat

Protected by a 120-strong Security staff.

It was basically a small army.

Meigs: imagine the paradox Of this place.

Escobar wants it to be A lovely family retreat,

Swimming pool for the kids.

Meanwhile, he's got shipments of Drugs and cash moving through.

He's got the place surrounded By armed guards and seaplanes

He's got the place surrounded By armed guards and seaplanes

And speedboats Coming in and out.

It can't have been the most Relaxing spot in the world.

Narrator: pablo himself was only Seen here in short flashes.

*

Interpreter: pablo was here, Two or three times maximum,

But he used to spend Only a few hours here and leave.

He wouldn't even stay Overnight.

When you're the seventh Richest man in the world,

You got you watch Your back at all times.

Narrator: By the early 1990s,

Narrator: By the early 1990s,

Escobar was embroiled In an all-out war

With the colombian government.

And after a stint in a Luxury jail of his own design,

He found himself On the run again.

With at least 80% of the u.S. Cocaine market

Supplied by his medellin cartel,

He was now a target not just For colombian authorities

And the u.S. Government, But also rival cartels.

And the staff at this mansion,

And the staff at this mansion,

Including security Guard william jiménez,

Were soon drawn Into the conflict.

In 1993, some of Escobar's rivals

Managed to infiltrate The compound.

Interpreter: what happened was That six more pickups

And one van Came full of people.

It was around midnight.

They placed two bombs, one on That side and one on this side.

Meigs: They stashed this huge quantity Of explosives in a bathroom

Meigs: They stashed this huge quantity Of explosives in a bathroom

And blew it up.

Interpreter: this is where they Placed the biggest bomb.

There was a huge explosion.

Everything you can imagine Was shaking.

In this area, There was a bathroom,

And that is where The bomb exploded upwards...

And destroyed The walls around it.

It was such powerful explosion.

Narrator: Who was behind this explosion?

And was this beginning Of the end for escobar?

*

Narrator: Outside medellin, colombia,

Is a dilapidated retreat

Once enjoyed by drug lord Pablo escobar's family.

In 1993, bombs were smuggled Into the compound,

Causing a huge explosion.

The organization thought to Be responsible was los pepes.

Short for persecuted By pablo escobar,

Short for persecuted By pablo escobar,

This was a vigilante group

Formed by victims Of escobar's drug war.

C.I.A. Documents released In 2008 suggest

Colombian intelligence officers Were in contact with los pepes.

Meigs: in fact, it was probably Funded by his rivals

In the cali cartel.

We'll never really know For sure,

But this bombing was kind of The beginning of the end

For escobar.

For escobar.

Narrator: Medellin became a battleground

For escobar's war of supremacy Against rival cartels

And also the colombian And american governments.

Escobar was offering Reward money

To anyone who would kill A colombian police officer.

So the bombing of this mansion Was too good an opportunity

For the police to pass up.

Police forces quickly Swooped in

And seized all the drugs And money

And seized all the drugs And money

Now exposed by The damage from the explosion.

Narrator: Though no one had been killed,

For william and many others

Who worked here At escobar's mansion,

The impact was Still devastating.

Interpreter: after the attack, Things were really hard.

Not because of the mansion Itself,

But because a lot of people --

I'm talking 200, 300 people From this area lost their jobs.

That was the hardest part to me.

Narrator: meanwhile, The net was closing in

Around the so-called king Of cocaine.

He corrupted the colombian Government

And law enforcement To a large degree.

Nonetheless, they still Came after him,

And the end wasn't Too far away for him.

Narrator: leading the manhunt Was colonel hugo martinez

Of colombia's national police.

Tracking escobar for years,

Tracking escobar for years,

He had turned down Various bribes,

His life under constant threat.

Martinez eventually managed to Pinpoint escobar's location

Using radio Triangulation technology.

*

A firefight ensued.

Escobar and his bodyguard Were shot down

As the fled Across the rooftops.

He died one of the greatest Outlaws in history,

The collateral damage there For all to see.

The collateral damage there For all to see.

Interpreter: As it happens, in most wars,

Many innocent people die,

People who have nothing To do with it,

And this has happened In medellin, in bogotá,

And in many Other places in colombia.

*

Narrator: Today, escobar's properties

Face a range of fates.

Face a range of fates.

Some have been demolished,

Others turned into theme parks,

But this ruined mansion Remains trapped

In a strange form of limbo.

Interpreter: at the moment, I'm in a legal dispute

With the government to have Ownership of this mansion.

I have been looking after it.

I have maintained and ensured

That no one else Would invade it.

Bell: Deciding on the proper use For a drug-funded property

Bell: Deciding on the proper use For a drug-funded property

And the profits from its sale

Is a touchy and legally Complicated subject.

To this day, pablo escobar

Remains a hugely divisive Figure in colombia.

There are those who still Revere him

As this national hero,

But for others caught in The crossfire, in the violence,

He represents everything wrong With the country.

*

In the thick forests Of wuensdorf,

In the thick forests Of wuensdorf,

On the outskirts of berlin,

Are what initially appear Like residential houses

Typical of this region.

*

Nusbacher: what looks like Pretty holiday cottages

That people ought To be vacationing in

Have clearly been Smashed to pieces.

Gough: the closer you look, You can't help but wonder

If these are just Residential houses.

The smashed concrete is Exceedingly thick,

And in some places, Clearly reinforced.

And in some places, Clearly reinforced.

Nusbacher: They're entrances to something That is much, much bigger.

Underneath these charming Destroyed houses

Is clearly something A bit sinister.

Narrator: Deeper beneath the tree canopy

Is an Innocuous-looking building.

Access to it however, Is far from ordinary.

There's almost a feeling here Of entering into a secret vault.

There's almost a feeling here Of entering into a secret vault.

Gough: whatever they were doing, They were clearly trying

To disguise and conceal This from the world.

Narrator: This complex has been home

To several of the world's Most powerful armies,

As director of the site Werner borchert reveals.

Borchert: I think this Location's really fascinating

Because there is no other place

Where the german kaiser, Later hitler,

And then the russians have left Their military marks.

Narrator: in september 1939, It was the turn of the nazis,

Narrator: in september 1939, It was the turn of the nazis,

And the date Was no coincidence.

This was one of the most Important communication centers

For the german army During world war ii.

And guess what --

It was finished just in time For hitler's poland campaign.

*

Narrator: this is maybach 1, The headquarters

For the high command Of the german armed forces,

And at its core, The zeppelin bunker.

And at its core, The zeppelin bunker.

The communication facilities

And the command and control Facilities in these bunkers

Are absolutely The beating heart

At the center Of the nazi war effort.

It's essentially very close

To what the pentagon Is in washington.

Nusbacher: In the english-speaking world,

We are really fascinated

With the way That the enigma code was broken.

And the zeppelin bunker Underneath germany,

And the zeppelin bunker Underneath germany,

This is where all the messages Came from

That we were listening to and Breaking at bletchley park.

*

Narrator: But does all this smashed Concrete and mangled metal

Indicate that allied forces Managed to find and destroy

This central communications hub?

*

Narrator: in thick forests Outside berlin

Is a bunker system that Functioned as the nerve center

As the of the nazi War effort in world war ii.

But this site was well-hidden From prying eyes.

Made to look like Civilian houses,

They were given shingled roofs And plastered walls.

They had fake windows,

And the steel-armored doors Were covered with wood,

And the steel-armored doors Were covered with wood,

So they looked like Just ordinary household doors.

Narrator: Heavily disguised,

They were Also built low to the ground

And scattered across a large Area in thick pine forest.

Corum: they are not laid out As you would expect.

This, from the air,

Does not look anything Like a military installation.

Narrator: At the midpoint of world war ii,

The allies Were in danger of defeat.

A direct hit on this facility Could make all the difference.

A direct hit on this facility Could make all the difference.

If you're going to try to bomb This complex,

It actually requires a little More difficult navigation

Than it does on a city

Where you'd have A very clear radar return,

You would have landmarks, Such as major rivers,

That you can use as A reference point for targeting.

But you have something On the outskirts,

It's harder to find Those reference points.

Narrator: Away from the glare of berlin,

Narrator: Away from the glare of berlin,

Finding it presented Allied bombers

With a serious challenge.

Added to the fact that they Appeared from the air

Like the homes Of innocent civilians,

Much of the facility Was buried beneath ground.

A ring of subterranean tunnels Connected all 12 house bunkers.

These, in turn, were linked To the zeppelin bunker,

Which covered an area of 50,000 Square feet across two levels.

Which covered an area of 50,000 Square feet across two levels.

With walls over 10 feet thick

And encased in an overall Protective concrete shell,

Construction workers Were only allowed

To work on-site for short stints

So as not to gain Too much knowledge of its scale.

Yet a stroke of luck Would finally reveal

This secret location To the allies.

We have records in The u.S. National archives

Of interrogations In february of 1944

Of interrogations In february of 1944

Where communications people

Who've been captured are talking About this bunker

In the countryside near berlin.

Narrator: at this point, Allied intelligence

Finally realized This compound's significance.

Finding and destroying it -- That was another question.

*

It took the u.S. Army air force The better part of a year

To pinpoint the location of The german army command bunker,

To pinpoint the location of The german army command bunker,

And they put in a serious raid On it, a big raid.

Narrator: 675 u.S. Planes Came swooping in

On march 15, 1945.

Could the u.S. Air force Break communications

To the front lines And cripple the nazi war effort?

Of the 20 people who died here, All civil population.

Because the civil population Was not protected by a bunker...

Because the civil population Was not protected by a bunker...

Narrator: despite These civilian casualties,

The facility was left With barely a scratch,

Communications disrupted For only a few hours.

But by april 1945, It was the soviets

Threatening to destroy This compound.

The red army tanks Advance so rapidly

That the germans have no time To put together a plan.

Narrator: adolf hitler was Shocked to hear soviet tanks

Were less thank an hour From maybach 1.

Were less thank an hour From maybach 1.

The german army's high command Was about to be crushed.

It turned out that the soviets Had to pause

To refuel with more diesel,

So the whole headquarters Bugs out

While the soviets Are refueling their tanks.

Narrator: having refused Evacuation before,

Hitler now signed off the Relocation of the headquarters.

As staff fled, they were Mistakenly attacked

By their own planes.

By their own planes.

Meanwhile, the soviets rolled Into the compound unopposed.

And what did they find?

Allegedly, four men.

Only four, three of which Surrendered immediately.

The fourth was too drunk To know what was going on.

Narrator: much of the valuable Equipment was dismantled

And sent to the soviet union,

Where stalin wanted a similar Complex built for himself.

But according to the potsdam Agreement of august 1945,

But according to the potsdam Agreement of august 1945,

The soviets were compelled To blow up

Captured military installations.

They did just that, But in a tactical way.

Nusbacher: they blow up a lot of Stuff on the surface,

But they leave a lot Of the tunnels

And a lot of the bunkers.

As soon as you go downstairs,

You see that the soviets Were clever enough

To leave the guts Of this installation intact.

*

*

Narrator: the soviets eventually Renovated zeppelin

And the tunnel system To house

Their high command Of soviet troops in germany.

They even upgraded the bunker To be nuclear-proof.

Nusbacher: this bunker was going To be the command post

For the soviet Destruction of nato.

This command post was going To be the place

Where the commanders Who destroyed europe

Where the commanders Who destroyed europe

In world war iii Would sit in order to do it.

Narrator: thankfully,

World war iii Never came to pass.

But the last russian soldier Only left in 1994,

After decades of fear And uncertainty

Through the cold war years,

When world war iii Felt like a very real threat.

*

Today, the ruins of this complex Provide a fascinating window

Into warfare through the ages.

Into warfare through the ages.

Borchert: make not war again -- This is our message here,

And that's why we present The military past here

In zossen-wuensdorf. That's the reason.

That's our message -- Make not war again.

*

Narrator: In the south of portugal,

Just a few miles from the border With spain,

Is a place with An otherworldly appearance.

*

*

Jerram: it's almost like a scar Has been opened up.

You've got the lovely greenery Of the ground around it,

But in this middle area,

This sort of swath of deserted And destroyed landscape.

Meigs: you've got all these Interesting colors.

You've got these black heaps.

You've got yellow bands.

You've got this reddish water.

And it's quite beautiful In a way,

But also kind of sinister Because these colors,

They're not supposed to be here On the surface of the earth.

They're not supposed to be here On the surface of the earth.

*

Narrator: spread across this Barren landscape

Are gutted buildings, forgotten Scraps of old rail tracks,

And strange towers On the brink of disintegration.

*

But the decaying structures

Are far from The most alarming sight.

The water itself Is dark and eerie,

With this kind of red rim Around it.

It's all very, very stark And a little bit crazy.

It's all very, very stark And a little bit crazy.

Auerbach: The whole area -- the buildings,

Their damage, Their degradation --

There's the sense that Something poisoned them,

And it poisoned the land, too.

Narrator: so what created This hellish landscape?

And why does it remain A scarred territory to this day?

*

The scorched earth and decrepit Buildings of this site

The scorched earth and decrepit Buildings of this site

Are not the only marks Left on this land,

For just nearby is A small cemetery

That holds the clue To who was behind all this.

Meigs: here we are in the middle Of portugal,

And here's this old graveyard,

And the names on the graves Are all english names.

Auerbach: we don't necessarily Think of it now,

But back in the 19th century,

Portugal and spain were really A land of opportunity.

There were riches In the ground there,

And the english wanted them.

Narrator: but what were The english searching for?

And why does this site Remain lifeless today?

*

Narrator: In the 19th century,

An english company leased this Land in southeastern portugal

And began mining.

But they weren't the first To recognize the value

Hidden below, as joao rolha,

An officer for the local Municipality, explains.

Established in the 1850s

And stretching for miles across The local alentejo landscape,

This is the sao domingos mine.

Meigs: this mine was a massive Industrial operation,

And in order to run it,

They needed to make huge Investments in infrastructure.

Auerbach: this is going to be The first place in portugal

Auerbach: this is going to be The first place in portugal

That has a railway line Extended to it.

It's gonna be the first place In portugal

That has electricity.

Meigs: And all the way down the valley,

You have these various Processing centers,

A rail line that would carry The materials from the mine,

And ultimately going all the way Out to the coast, to the port.

Narrator: the new investment was Creating jobs

And advancing industry Across the region.

But the state of the land today

Shows that not everything Was positive.

Shows that not everything Was positive.

This is going to bring portugal Into the modern times,

But it's gonna come At a terrible cost,

And its legacy is gonna be A frightening one.

Narrator: clearly, there was Money to be made here.

But the clue to What they were after

Comes from The disconcerting-colored water

That lingers in pools Across the site.

Meigs: normally, when you're out In the countryside

And you see a body of water, It's a very attractive thing,

And you want to go for a dip.

And you want to go for a dip.

You see this pool of black, Reddish water --

Clearly, something's Very wrong with this.

Narrator: incredibly, Just a few years ago,

This pool of dark water Somehow caught on fire.

This pool of dark water Somehow caught on fire.

What ignited the fire Remains a mystery,

But the coloration helps reveal What was being mined here

But the coloration helps reveal What was being mined here

And starts to explain why This land remains scarred today.

When I see red coloration Like this,

I immediately think of iron.

The water's highly contaminated With a lot of iron oxide in it.

But I know that it wasn't iron

That they were after In this particular area.

When the british came in, They were looking for a variety

Of valuable things -- Gold, silver, copper.

These things often tend To travel together in geology.

These things often tend To travel together in geology.

Ultimately, they focus On the copper.

Narrator: The 19th century was a time Of huge change across europe.

But while the threat of portugal Being left behind was very real,

This mine was doing its best To drag the country

Into the industrial revolution.

Jerram: copper is a very Desirable metal.

It has lots of good properties.

It's highly conductive, And it's got thermal properties.

And in the late 1800s, It was being used for wiring,

And in the late 1800s, It was being used for wiring,

The advent of electricity, And so on.

It was really quite A desirable metal.

Narrator: but to keep this place Profitable,

It would soon Have to be adapted.

Meigs: later, they focused On the sulfur,

Which is really just A contaminant in the copper.

But in the 20th century, They discovered

That sulfuric acid

Was very valuable in all kinds Of industrial processes,

Like making fertilizer.

So they started mining This just for the sulfur.

So they started mining This just for the sulfur.

Narrator: The crumbling towers and ruins

Show what's left of The infrastructure of this mine.

But it was the extraction And separation

Of the metals and chemicals

That left the true wound Deep in the earth below.

You have to process the rocks, So they needed a lot of water.

They needed to heat and smelt These particular minerals

To essentially remove the copper From the compounds

That they're associated in.

Narrator: the contaminated water From that processing

Narrator: the contaminated water From that processing

Had to go somewhere,

And the land began to absorb it.

*

Meigs: while they were pumping Out the water,

They were also pumping out All kinds of toxins,

And lord only knows What happened to people

That lived downstream.

Narrator: As the devastated land suggests,

Dark days were on the horizon.

*

Narrator: Early in the 20th century,

With the sao domingos mine In full flow,

Contaminated water From the processing

Was leaving a trail Of destruction in its wake.

*

Meigs: When you mix sulfur with water,

You get sulfuric acid -- Battery acid --

Incredibly dangerous, Toxic stuff.

And this landscape, you can see,

Is polluted with this From top to bottom.

Narrator: not only was The ground poisoned,

Toxic gases from the sulfur Would have been filling the air,

As well as the lungs Of the workers.

Eventually, the workers Are going to really start

To feel the effects of that.

The stuff being pulled Out of the ground

Is going to burn Their equipment.

It's going to burn Their clothes.

It's going to burn Their clothes.

It's even gonna burn their skin.

*

Narrator: but while the workers And their health

Suffered through the years,

Their welfare was never the Priority for the mining company,

As they found out When the mine closed in 1966.

Narrator: Both the mine and the people Of this area had been abandoned.

Narrator: Both the mine and the people Of this area had been abandoned.

Today, there is hope

That through an extensive Cleanup operation,

The land can be transformed For the better.

But it's a daunting task.

You know, you've heard the term "Fire and brimstone"

To describe hell.

Well, brimstone is the Old-fashioned name for sulfur.

So when you see a place Like this polluted with sulfur,

It really is literally A hellish environment.

*

*

Narrator: on the coast of kent In southern england,

Strange formations Unexpectedly emerge

Out of an otherwise empty Marshland.

Meigs: you come across these Giant concrete structures

Looming up out of the ground

Like some kind of A concrete satellite dish.

Selwood: There's something otherworldly And ethereal about them.

Selwood: There's something otherworldly And ethereal about them.

They're eerie, as if they come From another age.

Osborne: I first saw these when I was a teenager --

These strange, Science-fiction-type objects,

Miles from anywhere.

Narrator: two saucer-like Constructions sit alongside

A huge, curved wall Set amongst peaceful lakes.

These are strange concrete Structures out in the marshland

Along the coast With apparently no real purpose.

Along the coast With apparently no real purpose.

Selwood: they give absolutely no Sense of why they're there.

Corum: 99% of people, even the People that live there,

Probably have very little idea What these things are.

Narrator: the simple appearance Of these constructions

Belies their Technological importance.

Corum: These are concrete structures,

But they are very sophisticated Early-20th-century technology.

But they are very sophisticated Early-20th-century technology.

And it was all driven By world war I.

[ machine-gun fire ]

Narrator: Long-distance artillery fire was The key weapon of world war I.

Microphones were used to try And get a fix

On the location Of artillery guns.

Known as "Gun ranging," Similar technology is used today

By u.S. Police to Triangulate incidents

By u.S. Police to Triangulate incidents

Involving gunfire In major cities.

As the great war progressed,

Innovative sound-detection Devices were developed

To meet the challenge Of new technology in warfare.

But the position of these Structures, pointing out to sea,

Clearly show that artillery fire Was not their primary concern.

The location of these Structures --

Right on the coast, facing, Overlooking the channel --

Right on the coast, facing, Overlooking the channel --

Gives you a clue As to their purpose.

Meigs: They were built to pick up

The sounds Of approaching enemy aircraft.

Even a few minutes Of extra warning

Before those planes Become visible in the sky

Could make a massive difference On the ability

To get your planes in the air To defend the country

And to get your civilians Into shelters.

Narrator: could these concrete Monoliths help save britain

In their most Desperate time of need?

In their most Desperate time of need?

*

Narrator: On the southern coast of england

Are three initially baffling Objects in an empty marshland.

These are the denge Sound mirrors,

Rare survivors of a chain Of acoustic listening devices

Built along the south coast of England in the interwar period

To detect incoming Aerial threats.

Near the tip of a headland At dungeness,

Near the tip of a headland At dungeness,

They lie just 25 miles From the french coast

And the european continent.

There is no other major source Of sound or distraction nearby.

You can focus out at sea On sound.

Osborne: The simplest way to understand

How the mirrors worked Is what you do yourself.

If you want to hear something, You do that.

And that's simply What the mirrors are.

And that's simply What the mirrors are.

They're a much larger version Of that.

They concentrate sound to the Sound collector and amplify it.

*

Narrator: the first giant mirror Was constructed in 1928,

Designed by gifted Physicist percy rothwell.

Lessons were quickly learnt.

A larger, 30-foot mirror, Built alongside the first one,

Was set at a different angle.

This gave no advantage In terms of range,

This gave no advantage In terms of range,

But it could track The trajectory of aircraft

With greater accuracy.

Then, in late 1930, They went one step further.

The star of the show Was the long mirror.

This was 200 foot long And 26 foot high --

By far and away The largest structure

Of its kind ever created.

It wasn't just a big wall Of concrete

That you stood in front of.

It was actually a very Sophisticated scientific device.

Narrator: the curved surfaces Concentrate the sound waves

Narrator: the curved surfaces Concentrate the sound waves

That bounce off the walls,

Focusing the waves onto A sound collector or microphone.

An operator stationed In front of the mirror

Would use a stethoscope

To find the direction Of the sound source,

Moving the sound collector Inside the mirror bowl.

The results were Cross-referenced

With those of other mirrors

To calculate an aircraft's Height, speed, and flight path.

While the sound mirrors Look basic or even crude,

While the sound mirrors Look basic or even crude,

Actually operating them Was an incredibly skilled job.

To distinguish between The sounds

Of different sorts of engines -- Some aircraft, some ship --

And other noise was Incredibly difficult work

And required such focus And intensity

That operators could only work In shifts of 40 minutes.

One of the limitations Of the acoustic technology was,

Of course, it collected An amplified all sound.

If there were Closeup bird noises,

If there were Closeup bird noises,

That would often be collected

Instead of the aircraft noise That they were searching for.

Narrator: to intensify The challenge even further,

Aviation technology Was developing

At an extraordinary rate.

The new and higher speeds Of aircraft

That you're getting by The late 1920s and early 1930s,

And you're talking About new cowlings,

Less drag, powerful engines.

So your speed is virtually Doubled.

So your speed is virtually Doubled.

Zeppelins traveled at about 60 miles an hour

And made a hell Of a lot of noise,

So they were very easy to track.

But once you got on further Than early 1930s,

You've got aircraft traveling At around 200 miles an hour.

You've got fighters traveling At over 300 miles an hour.

And so even if you can get 12, 14, 15 miles' warning,

You're only talking about A couple of minutes.

Narrator: With tensions growing and the Rise of fascism across europe,

The threat of another world war Loomed large on the horizon,

And hitler was investing heavily In his new air force.

And hitler was investing heavily In his new air force.

The other difficulty was The immense advances

In aeronautical technology Under the nazis.

The speed of aircraft increased Very rapidly,

Which meant that the job Of detecting in time

Was increasingly difficult.

Narrator: Would these sound mirrors Provide adequate warning,

Should hitler's new fighter Planes come roaring

Across the english channel?

Corum: so, you have relatively Little warning time

With a sound system.

With a sound system.

But the development of radar Has been coming apace,

And it is ready to take over Just at the time

That aircraft Are becoming too fast.

This new technology has been Developed to the point

That you can emplace It along the british coast

And take over from The sound detection.

Very soon after the development And installation

Of the acoustic mirrors, Radar was invented in 1935.

And that was such a futuristic Technology

And that was such a futuristic Technology

That it made the sound mirrors Instantly obsolete.

Meigs: they look almost like Some kind of ancient monument.

And in a way, They are monuments.

They're monuments to A defunct technology.

Narrator: While they were quickly Rendered obsolete by radar,

Their development Was not in vain

And would prove pivotal In the battle of britain.

Corum: you see, it wasn't just The technology

That was key In the battle of britain.

It was the organization That was behind that.

It was the organization That was behind that.

All that radar did was it gave Much greater accuracy and range

To an already existing Communication system

That went back To those headquarters,

Hubs that coordinated the ground

And the air defense That worked so well,

And kept britain free And saved the world in 1940.

Narrator: Today, these old devices sit In a protected nature reserve

And provide a fascinating Glimpse into a bygone era.

And provide a fascinating Glimpse into a bygone era.

Osborne: although the mirrors Are somewhat

Inaccessible on these islands

And only open to the public once Or twice a year,

That has a benefit of preserving This little piece of history,

Which otherwise must surely Have perished.