Original subtitles

- [Narrator] The Nazis carved an underground city,

hidden in the forest of Poland.

- The woods are concealing something really profoundly dark.

- Miles of tunnels burrowed into the mountainside.

- You really can only tunnel

through this material with drilling and blasting.

[blast exploding]

- [Narrator] So much remains unknown.

- You look at these tunnels, it's eerie.

There's still materials, equipment left.

It looks like people left in a rush, in a way.

- Most people think that there could

be hidden German technologies.

- It's built at such a scale that you

can drive trucks through them.

- [Narrator] Whatever was stored here,

it would have been immense.

- There is something; it looks like wooden crate.

- The only way to solve it is to keep digging,

keep exploring. [dramatic music]

- [Narrator] Deep in the heart of Poland,

hidden in the heavily forested mountains,

a secret project on a huge scale is undertaken by the Nazis.

- The Owl Mountains are kind of misty and dark and shrouded.

Very few people live there.

It's a kind of ancestral forest,

more remote than you imagine for the area in Europe

in which they're located in Silesia.

The woods are concealing something really profoundly dark.

- [Narrator] 1943, the tides of world War II

are turning dramatically.

Germany is on the retreat, but the war was far from over.

The Owl Mountains cover an area of about 77 square miles,

near the historic lower Silesian Region.

- If you are in this mountains, you see nothing.

You see some small holes on surface,

some small pieces of concrete,

some structures that you cannot identify in any way.

- [Narrator] Here, the Nazis put into action

a tremendous construction project known

as the Osowka Complex.

Even with the monumental resources being poured into it,

they do so in complete secrecy.

- It's certainly clear that the Nazis were using

that location, sheltered and remote from the populace

and also from Allied bombing.

- The Nazis did not want people to know about it.

The entrances to many of these complexes had shrubbery

and vegetation to try to hide them.

- [Narrator] Absolute secrecy is critical for this project.

No one, not even locals, are allowed near the mountain

for fear of spies and informants.

- To be able to keep it a secret,

what do you say to someone when they ask,

why are you blasting the side of the mountain?

- The public would not have known very much about this.

So the public learned what Hitler,

Goebbels and others wanted them to know.

- In fact, those people did not realize what do they build.

There were some gossips they heard, but of course,

the purpose was secret.

- [Narrator] Locals are merely told that

The Silesian Industrial Company was created

to conduct construction work.

- The Nazis were just obsessed with secrecy.

They had a cult of paranoia and that was everywhere

one went, the SS or the Gestapo had eyes

and ears on every project and every person.

- [Narrator] With the war going badly on so many fronts,

the construction of this massive complex is baffling.

- The project has the official involvement of Albert Speer,

who is one of the right hand men of Adolf Hitler

and certainly, in architectural design.

So it has all the hallmark of a Nazi orchestration

at the very top levels.

And that feeds the questions about what it was exactly for.

- Many of the projects they built seem to be unbuildable,

undoable, unrealistic.

Yet they managed to somehow build these massive facilities.

And what's even more shocking is they did this in the middle

of a war and while building dozens, if not hundreds,

of similar structures all across the continent.

It boggles the mind.

- [Narrator] Though the project is top secret,

experts believe one important clue is the makeup

of this specific terrain.

- The Owl Mountains are igneous rock

and igneous rock is the old core of the earth,

the oldest rocks that are on the face of the planet.

- The rock that you can't easily excavate,

that you can't easily use hand tools to remove,

that takes a lot of force to shatter and move through.

- [Robert] They're very dense.

They're not at all like sedimentary limestones.

These rocks are very difficult to bore through,

very difficult to tunnel through.

- You really can only tunnel through this material

with drilling and blasting.

[blast exploding]

It's an intensive effort.

- I can't think of how much energy you would need

to blast that rock.

That's a lot of power.

- So there must've been a very good reason

to build this facility here than anywhere else.

One of the advantages of tunneling

through igneous rock is that it's so hard

and so solid that it pretty much supports itself.

- And for that reason,

they're also extremely resilient to any attacks.

[bomb exploding]

- Once you get deep inside that mountain, you're good to go.

You are protected from almost anything.

- [Narrator] Creating this impenetrable site here required

an astounding workforce to carry it out.

And one that could also keep silent

about the facility itself.

13,000 forced laborers and prisoners

from concentration camps were put to work,

digging out the Osowka Complex.

- What you could achieve with 13,000 workers,

in sync, being directed and focused on a task.

You can move pretty quickly.

- Many of the thousands of forced laborers that died

in these tunnels were killed by the disregard

of the Nazis for safety of those workers.

- You're working possibly under suspended loads that

could give way at any time.

You are working in very wet and mucky conditions.

You're inhaling, potentially, a lot of particles,

but you don't have the safety equipment

that you should be using.

- Third Reich had, almost till the end,

unlimited human resources, slave workers, forced laborers,

concentration camps inmates.

So they had so powerful and huge working power.

- [Narrator] With this massive force of slave labor

at their disposal, the Nazis proceeded to remove upwards

of 70 million cubic feet of rock from the landscape.

- It's a mountain of itself, right?

You're taking a mountain out of a mountain.

- So we're talking about moving 10s of millions

of tons of material out.

To put that in perspective,

an average dump truck holds probably, maybe 20 tons.

So we're talking about hundreds of thousands

to millions of dump truck loads of material.

- [Narrator] With very few records to shed light

on this project,

experts attempt to pry answers from the rocks themselves.

- I spent 15 years researching

and exploring places like Owl Mountains.

And as far as we know,

it should have many underground complexes connected

to each other as a one system.

- [Narrator] But the layout and extent of the structures

are confusing and deceiving to those who explore them.

- In that era, there wouldn't have been very many tunnels

that had reached that length.

So it would have been a major undertaking.

- [Narrator] Even more baffling is the daunting scale

of the construction.

- One of the first things one notices

is the absolute size of this project.

It's massive in its scope.

- And obviously built at such a scale

that you can drive trucks through them.

- [Brooke] They're for a lot of traffic to flow through.

- These are not bunkers and tunnels.

These are underground cities.

- If you want to build tunnels of this magnitude,

you've got to deforest, you've got to clear the land,

you've got to provide a clean water source.

You've got to build roads into this area that can support

this heavy equipment that you need to bring in.

You need to build machine shops,

bunkers and barracks for people living there.

And those alone are a project.

- It would be difficult for any government today

to build this, not only the science and the engineering,

but think of the cost.

In today's dollars, we're talking billions of dollars.

It's hard to imagine any of these projects

being done today by virtually any government.

- [Narrator] Even as they fought a retreating battle

on multiple fronts,

the Nazis concentrated enormous efforts

to construct this massive system and do so quickly.

- They advanced these in two years.

That is an incredible feat.

Moving those at that rate is madness.

The amount of manpower and planning

and logistics behind that, it's crazy.

- And this is 75, 80, 85 years later,

they're still in good shape today, many of them.

The one thing the Germans knew how to do was build.

- They built the system in a protected area.

This was a strategic place to build something

that was important to them, that they needed to protect.

- [Narrator] And it's precisely then purpose that

has many experts coming up with different theories.

- And at the end of the day,

you can come up with fabulous notions of what it was,

but you need some sense of fact, you need documents,

you need evidence to prove precisely what it was used for.

- We don't have a lot of knowledge

from the people who built it,

in part because it was concentration camp labor

and many of them were murdered.

And we don't have a lot of information from

the local German populations because they

were all fleeing the Red Army in 44, 45,

or they were expelled after the war.

So all of the people who may have been intimately connected

with the plans for any of the tunnel systems

or could have been able to tell us how some

of this stuff fit together,

they disappear after the war and the documentation,

a lot of it appears to have been destroyed.

- [Piotr] We cannot say for sure that all those structures

and all those tunnels should be connected.

- [Expert] You know, on one hand,

the Owl Mountains are full of natural resources

and ores and things that the Nazis need

to make the war machine function.

But on the other hand, the amount of time and energy,

the cost of digging through just layer

and layer of solid rock, it really makes no sense.

- [Narrator] Researchers attempt to piece together clues

as to what the Nazis intended and following a suspicious,

blocked opening, what is discovered to be an elevator shaft,

leads through the mountain, bank into the forest,

and comes up just near a ruin known only as the casino.

[dramatic music]

An impenetrable underground Nazi city appears to

be known only to very few in the hierarchy.

- The Nazis were obsessed with secrecy.

They were obsessed with keeping information to themselves

and not allowing people who weren't directly involved

in the project from knowing anything about it.

- [Narrator] Part of this top secret complex

is hidden behind trees and foliage.

Known only as the casino, this building connects

via an elevator shaft to the larger complex.

The building known as the casino

at the top of the mountain is rather strange looking,

but by all accounts, it looks as though it could have

been some kind of command bunker

or perhaps an observation station.

- [Narrator] This 160 foot long building juts out

of the ground with walls 20 inches thick.

- It's a concrete bunker, it's a tank.

It looks pretty bomb-proof.

Very small window openings, barrel formed roof,

and it connects directly down to the tunnels.

- [Narrator] It also features chimney ducts,

an electric grid and a nearby train stop with

an elevator shaft leading to the tunnels below.

- [Expert] You're really kind of like you're

in a concert hall almost, except it goes on and on and on.

- [Narrator] Not far from the casino,

another abandoned ruin gives way to more secret plans.

Experts only know this was a power station,

but used to power what?

- You need electrical generators

and a power plant that can operate independent

of whatever power plant would be in the area.

- There was a lot of effort done to get rid of evidence

that would have helped us understand what the structure is.

- Could it have been for developing a new weapon

that was gonna win them the war?

- Some people believe that all surface structures

at Osowka like casino,

it was kind of a platform for the first reactor

that Nazis could build in those mountains.

- [Narrator] Rumors have long persisted that

the Nazis were on the cusp,

if not already in possession of atomic weapons capability.

- If I really wanted to develop some technology

that was well beyond what my enemies were developing,

I would want some type of complex like this

that would keep prying eyes away.

You can control the flow of people to

and from that complex relatively easily.

Obviously, it can't be photographed by aircraft flying over.

- There is not many stories about what could be stored

in those tunnels, but most people think that there could

be hidden some German technologies.

- Conspiracy theories that these were designed,

at least in part, to be underground facilities

for further production of secret weapons is quite tenable,

which would be consistent with things where

they took production of rockets

and advanced scientific experiments

and tried to put it underground,

both for protection and for further development.

- We know for sure that the Germans

had moved industrial facilities underground.

The airplane engines were being built underground.

The rocket program, the production,

was moved into underground facilities.

And so, it stands to reason that some of these tunnels

could have been designed as places where

they could continue to manufacture supplies.

- [Narrator] When the decision was made to abandon

the complex, they apparently did so in a hurry.

- When you look at these tunnels, it's eerie.

There's still materials, equipment left.

It looks like people left in a rush in a way.

- When you see these wagons and hand tools,

chains, almost littering some of the tunnels,

it does make you feel like something happened here

to make people suddenly leave.

It's got quite an eerie feel to it.

- [Robert] It ran out of steam like the Third Reich itself

towards the end of 1944, 45,

when the Soviet army starts advancing.

What we do know, without doubt,

is the resources that went into it.

- [Narrator] While Piotr has explored many previously

unknown parts of this underground labyrinth,

there are still areas he has yet to crack into.

- Now is a guardroom on the beginning of the complex.

And it's blocked from each side.

So, since World War II, nobody looked down there,

and there is a little hole I will try to put

the inspection camera to see what's inside.

Every time we put this inspection camera

inside unknown space, I'm excited.

It's natural because I still hold that

we'll finally find some solution,

we will find another part and we will discover

something important to the mysteries of the Owl Mountains.

There is something, some parts of wood,

some rocks, some parts of concrete.

- [Narrator] Piotr, like many experts,

believes what we see is just a small portion

of the construction.

- There are rumors that won't go away

that there are indeed more tunnels and more complexes hidden

in the mountainside around the Osowka Complex.

- We do not know how that tunnels should look like

when they would be finished.

We can not even imagine, because we do not have a plan.

- We know that the Nazis were planning to redevelop

these tunnels and develop them further.

We know that they ordered a huge amount

of concrete for this project.

We know that the precise purpose

of these tunnels is still not clear.

It wasn't even clear to senior members

of the Nazi high command.

So all in all,

you've got a mystery wrapped up within a mystery

and the only way to solve it is to keep digging,

keep exploring, keep going down into these tunnels.

- It's really hard to say what is exactly.

We just see a little part of the room.

We see that it is blocked.

I will try to put camera, to dig another hole

to see the space inside from different perspective.

- Just taking a short cord.

we are inside.

- It is not easy because we have a free holes

that we can do it.

Definitely inside are some items we

can't identify at this moment.

What can it be?

- [Narrator] No one has laid eyes on the room

since 1945 when the Nazis fled.

- It looks like crate, wooden crate.

If you want to see more, we have to put more lights.

That will give us view fr details inside.

- [Narrator] As Piotr continues his investigation,

another theory emerges.

The large presence of SS in and around the complex

led many to believe this could ultimately be

a massive command bunker for none other than Hitler himself.

[dramatic music]

Digging in the Osowka Complex,

researchers attempt to discover rumored missing caverns

and tunnels and ultimately decipher the purpose

for this massive undertaking.

The scope of secrecy and the huge presence of SS

lead many to believe this was intended

to be a fuhrer command headquarters

for Hitler himself.

- It stands to reason that if the complex was envisioned

as a fuhrer residence,

that some of these tunnels might fit those priorities.

You could have had a train coming through those tunnels.

So they would have had to be big for that reason.

- [Narrator] Hitler had many other bunkers.

Could they yield clues to the mystery

of the Osowka Complex?

- Most of the theories are that it was the fuhrer bunker,

that it was created for at Adolf Hitler as

a frontline position to command the authorities

of the armies in defense of Germany.

- Albert Speer wrote, after the war,

that it was supposed to be a regional administrative center

with a fuhrer headquarters and industrial facilities.

But people don't necessarily believe him

because he often was suspected

of trying to throw people off.

- [Narrator] Hitler was known to have spent much

of his time supervising the war effort from within bunkers,

such as the Berghof, Wolf's Lair and Wolf's Lair II.

- There was a desire for Hitler to be closer

to the front lines.

So it makes sense that the fuhrer headquarters would

be positioned in places that had something to do

with the war effort.

As commander of the armed forces, he moved around.

He tended to move where there was a battle

or a fighting front.

- The Nazi's stunning military successes at the start

of the war mean that Hitler's got

a pretty good working relationship with his generals.

He trusts them.

But as the war starts to turn against him,

Hitler becomes increasingly more paranoid.

Not only does he think his generals are incompetent

and frequently replaces them,

but he starts to believe that

that actively plotting against him,

culminating, of course, in the attempt on his life.

Well, for Hitler, this is proof that only he and he alone

is the supreme military commander can run this operation.

He is quite literally ordering units

into attack to stand their ground.

He's issuing orders that go right down

to captains, lieutenants, majors.

And we're not just talking generals.

He's running this war himself.

- His fascination with fuhrer bunkers is important

because he imagined himself, at various stages,

to be the military architect that he always wanted to be.

He thought that he was the great genius

behind German military strategy.

He was absolutely not.

And also that he would somehow inspire these heroic defenses

of Germany, particularly as the war went poorly

by being in places like the Wroclaw in Poland.

But if you sort of extrapolate from that

and try to imagine what these tunnels represent

as a fuhrer bunker, it's not really consistent.

- [Narrator] There are noticeable differences

in design between Hitler's oft used forward HQs

and the Osowka tunnels complex.

- This one is particularly massive

and seemed to imply multiple purposes.

- [Narrator] The Berghof was Hitler's headquarters

in the Bavarian Alps.

Later altered, it became his vacation home in 1935.

- The Berghof was also very outlandish.

So it starts out as a very small place based

on the fact that Hitler had a vacation property there

and places to store loot and wine.

And by the end of it,

most of the senior Nazis had villas there.

- [Narrator] But the layout of the Berghof doesn't look

at all like the Osowka Complex.

The Wolf's Lair, a two and a half square mile complex

on the Eastern front consisted

of three concentric security zones.

It housed some 2,000 people,

including some women who were required

to sample Hitler's food to test for poison.

- The Wolf's Lair, which was also in the East and

was a popular fuhrer headquarter was the site

of the 1944 Stauffenberg bomb plot.

- [Narrator] Known as Operation Valkyrie,

it was an attempt by conspirators to take control

of Germany and assassinate Hitler.

It failed.

- After that, the security around Hitler is stepped

up quite a bit, and it's possible, also,

that some of the more intricate structures would have

been part of an attempt to make these places far more secure

to protect Hitler, not only from being killed

by an enemy plane, but protecting access

to him so that no enemy within could get to him.

- [Narrator] Certainly, that could explain

the complexity of the Osowka complex.

- Other fuhrer bunkers are considerably smaller.

They're not anywhere near the heft or the size

of the scale or the scope and not as interconnected.

Sufficiently impressive defenses, I suppose,

but nothing along these lines.

They're not as cavernous, they're not as massive.

- The main differences is that mainly,

Wolf Lair is a on surface structure and all structures

in the complex are completely underground,

inside the mountains.

- [Narrator] Advances in imaging technology allow experts

to compare these ruins.

- They can't imagine you building facilities

that had interconnected railways and huge ceilings simply

to either have a command center for the fuhrer

or to protect the fuhrer.

- [Narrator] In addition to this massive complex,

looking so dissimilar from Hitler's other traditional

forward HQ's, he was rarely, if ever,

reported to have visited this location.

- One would expect that Hitler would frequently visit

this facility for what, today, we would call a photo op,

but that wasn't the case.

Hitler did not visit the site as often as you would expect.

Why; number one, it's secret.

He doesn't want people to know a lot about it.

And as remarkable as this structure is,

we need to remember it's one of dozens and dozens

and dozens of massive development and construction projects.

- [Narrator] while the Nazis destroyed or hid most

of the documentation, in their haste,

they did leave clues behind in the forest that

could shed light on this mystery.

An underground city is built by the Nazis,

as a defeat for Germany looms.

- There are miles of tunnels burrowed into the mountainside.

- [Narrator] While explorations inside the complex attempt

to reveal more hidden spaces,

a new clue is found in the forest nearby.

The few documents found specify massive amounts

of concrete were delivered to the site.

But upon inspection,

only a few piles of fossilized bags are visible.

- If you're managing a project of this magnitude,

you know how important it is to order your material ahead

of time, because nothing is worse than having all

of the forms ready to pour concrete

and the concrete isn't there.

So if it was ordered and it was transferred,

it's expected to be poured.

So where was it poured?

- There are some documents mentioning that a mound

of concrete should be spanned in those mountains,

should be somewhere there.

- The amount used in these tunnel systems

was 360,000 cubic yards.

It's the equivalent of a cube that's 210 feet on site

or 12 times the amount that went

into building Yankee Stadium.

- The Nazis didn't make clerical errors.

The concrete was here, it was sent here,

it was designed for this location.

- We know from documentation that this entire tunnel system

was supposed to be supported, but onsite, it is not.

There's only maybe 10% done right now.

So, they had intended to do a significant amount

of more work.

- And we do not see, in the structures, remains,

any sign of this concrete.

- [Narrator] During the construction of the Osowka tunnels,

the decision is made to hand control over

to Organization Todt responsible

for handling vast construction projects,

such as the Autobahn.

It's unlikely this concrete would have gone unused.

- Operation Todt was a part of a massive series

of organizations that managed concentration camp labor

and managed forced labor across the Third Reich.

And they were very effective at getting not only a lot

of labor onto major projects, but finding the kinds

of labor that was skilled in various aspects of a build.

- There are rumors that won't go away

that there are indeed more tunnels and more complexes hidden

in the mountainside around their Osowka Complex.

If more tunnels and underground chambers were discovered,

it might help piece together the puzzle.

- [Narrator] Today, initial investigations reveal

multiple intentionally collapsed and buried entrances

and shafts, potentially concealing massive sections

of the Osowka Complex.

- Presumably, the tunnels would have been dangerous.

Some of them would have been destroyed

by the retreating Wehrmacht.

Some of them were walled in by the Soviets,

which leads to a whole series of other questions.

- Why would the Nazis, after the war,

have gone to all the trouble of destroying these tunnels

to keep this place a secret?

- I'm incredulous that they would destroy tunnels

if there was any possibility of finding things

in those tunnels.

- Documents state there should be some more tunnels.

There's still a lot of hope that there must

be something more to detect.

- [Narrator] Penetrating igneous rock is a difficult task,

but modern technology might shed some light

on the tunnel makeup.

- The FLIR camera show us difference

between comparator in different spaces.

It's very useful in a close space.

Now is in the camera some empty space,

which have different temperature.

- [Narrator] Another method to detect underground structures

is ground penetrating radar.

- Ground penetrating radar is similar to normal radar

that we use above ground.

You emit a series of electromagnetic waves down

into the ground, which then bounce back off anything

that's beneath your feet.

And it's used to show you if there

are different materials buried in the ground,

and it can tell you how deep down they are.

So it can be used to detect things like pipe work or cables.

It'll often pick up lumps of concrete

or, occasionally, big voids.

- If we have a tunnel and the tunnel is blocked,

we trying to detect what is behind,

but we can do it only from the surface.

For sure, they could be below, but in each site,

in which direction.

So we do it sometimes blindly.

- [Narrator] Can Piotr's investigation involving GPR reveal

some truth to the tunnel's mystery?

- We've already made, many times,

such a scanning in this place and nothing special happened.

- [Narrator] But this time, something different.

- Surprisingly, we have a huge anomaly.

- [Narrator] Though he and others have thought

they had scanned this place many times,

an opening has been detected below the cavern floor.

- Everyone want to believe that below those structures

we know there are other which are unknown.

We hope that they still exist.

- [Narrator] Could this void be one

of the lost Osowka tunnels?

A team is using ground penetrating radar

in the Osowka tunnels,

hoping to find new clues to the complex.

Piotr has been exploring these tunnels for years

and has run several GPR scans in that time,

mostly with no results, but this time, he detects something.

- We was scanned by GPR system.

Surprisingly, in this moment, we have a huge anomaly.

I cannot explain it, but definitely,

we have some empty space below.

- [Narrator] Additional scans confirm a large void below

what is thought to be the bottom of the complex.

- I think a lot of geologists would probably

be quite excited discovering a void

that they didn't already know about,

like a tunnel or a cave.

So for example, if you were in these tunnels

using ground penetrating radar and you you'd mapped all

the tunnels out,

but you found a void beneath you that you didn't know about,

that would spark some interest.

- To definitely check what is below,

we would have to prepare drilling to have final proof

that there is something below.

The main thing that people still looking for

are missing tunnels because we all believe

that there is still more finished tunnels in the area.

- Really, what the goal would be to figure out how

to map that system in its entirety and piece together

what the various parts of it were gonna be used for.

- [Narrator] While experts continue to piece together

the tunnel system to get a bigger picture

of this grand complex,

experts look to the timeline of the war for further clues.

- While the war in the East initially goes very well

and the Germans advance,

the tide turns over the course of 1942.

- The Allied invasion at Normandy in June, 1944,

precarious as it was, spells the end.

- [Deborah] Soviets and the Western allies had not broken

the Alliance that so many Germans had been hoping.

- With the Soviets advancing at pace,

driving the Germans back,

it does seem odd that the Nazis would

then put so much effort into constructing

this secret complex.

- Why they're still pouring so much energy into it

when it's becoming increasingly clear

that they're going to lose the war.

And it also causes us to ask questions

about what they then thought they might use it for

in the event that the war was lost.

- [Narrator] Perhaps these tunnels were created

to house something truly unique.

- We know that the Germans started

moving important things underground.

- [Expert] Could it have been

for storing all their valuables?

- The Nazis envisioned themselves to be the defender

of European culture, not just of Germanic culture.

These were guys that had looted Europe since 1939,

millions of pieces of artwork, sculpture, paintings,

you know, you name it.

- [Narrator] As the pendulum of war swings

in favor of the Allies, the Nazis frantically search

for places to hide stolen artwork.

- This is the ideal place to hide all the things

that you've been stealing for years and years.

We're talking about billions of dollars of artwork.

Nobody would have known what was under here.

- And also, they were people that wanted

to gain tremendous personal wealth.

So there is a lot of substantiation to the fact

that these facilities may have been designed to harbor some

of these artifacts and lots of that artwork has never

been accounted for.

You're left with big, huge chambers that conceivably

could have been used for loot that Germans took from Europe.

- [Narrator] But some experts doubt the suitability

of the conditions for storage of delicate valuables.

- Tunnels aren't great for artwork.

They're high humidity.

Older pieces of art don't do well in humid environments.

They really do need careful temperature control.

So it's really not an ideal place for artifacts.

- [Narrator] If not for stolen treasure,

some researchers look to the extremely high presence

of the SS to explain the need

for such a huge scope and secrecy.

- Were people trying to think

of exit plans when it became increasingly clear

that the Germans were gonna lose the war?

Absolutely, they were.

- There are theories that the Nazis had planned

for one last stand, possibly to come into action

well after the war had finished.

- [Narrator] One of the rumored plans involves

a highly secret elite unit dedicated to carrying

on the fight no matter the odds.

- If you are looking for a place to secretly hide

and store both troops and equipment,

you can't deny that the secrecy and isolation

of the Owl Mountains would have been

the perfect place to do that.

- The system is built in a place that had once

been fundamentally part of Germany.

Did they envision that they were going to lose

this territory altogether,

depending on the outcome of the war?

Probably not.

Hitler had ordered, in certain places,

the Germans not to surrender

and to essentially create fortresses

that they were supposed to hold out in

as the Red Army came through.

- Strictly speaking, from a defensive position,

it would make sense to hold yourself

up in the Owl Mountains, relatively remote,

it's shrouded all the time

and hard to navigate in a kind of dark forest way.

But more importantly,

you're shoring yourself up within the frame of a mountain

and that affords you some degree of defense against weapons

of all sorts, right, against artillery and against bombing.

- If we see the wrench of this complexes,

how huge it was, in fact,

it could protect against even not conventional weapon,

but also against the nuclear weapon.

- The elaborate nature of the systems underneath

with interconnected, everything, you know,

that would be consistent with a last stand.

But it really does look like a place

where you're pooling all of the last resources

that you have and particularly the ones that you think,

in your madness towards the end of the war,

might tilt the balance.

- You're not talking about one or two people underground.

You're talking about thousands of people.

Therefore, the facility itself is only a small fraction

of the overall project.

There have to be piping,

there has to be tunnels that lead

in all directions to come above ground for ventilation.

There has to be fan systems.

There has to be an electric generator that

is supplying a lot of these systems.

So this was an enormous

and complicated construction project.

- We know that there were Nazi German leaders who

were encouraging the Germans to escape

into the mountains and carry on the guerrilla fight

against whichever enemy were there

and keep the Nazi flame alive.

Maybe this all was gonna be a part of this.

After all, the woods around it and the tunnels underneath it

make the perfect hiding ground for whatever continuation

these mad men wanted to have happen as the war ended.

- It's a heck of a place to hold up

what's left of your army and fight to the end.

That, to me, is consistent with a lot of the Nazi ideology

throughout the war as well as

the senior command right to the end.

- There's reason and purpose for these large spaces

to be filled with something, populated, like a city, almost.

- [Narrator] Whispers of a fanatical

and secretive unit persist.

Could the complex have been built as part

of a secret unit known as the Werewolves Operation?

As Hitler orchestrates his plans to keep fighting

in the face of an increasingly grim outlook,

signs point to the Osowka tunnels being

the site of a Nazi last stand.

Reports of an elite

and shadowy fighting force intrigue experts.

- The SS wasn't a singular organization.

It never was.

It had multiple units, I should say,

or departments within it.

And it rather infamously devised special forces

within its own ranks.

- [Narrator] Operation Werewolf was

a Nazi last ditch attempt to create secret units

to harass the advancing Allies

and Soviets behind enemy lines.

- The SS Werewolves are sort of infamous,

specially trained defenders of the most sacred places,

sort of the ultra hardcore of the hardcore Nazis as it were,

of the SS in particular.

- [Narrator] But whispers persist

of the plan going much deeper.

- The rumor was that the Werewolves were a branch

of the SS who were commissioned

with staying around in the region after the war,

engaging in a kind of a partisan fight

to destabilize the region even after the war was lost,

and also destroy any information related to the project,

to wreak havoc in the countryside

and to protect the secrets of the tunnel system.

- In that light, the Werewolves are kind of

the ultra fanatics that would be commanded

by the SS and report exclusively to the SS.

So this is somewhat of a legend,

that they were all dedicated past 1945.

- [Narrator] On April 1st, 1945,

the first array broadcast plays across radio stations,

starting with a howling wolf.

A hunting song would begin whose lyrics were

my werewolf teeth bite the enemy,

and then he's done, and then he's gone.

The broadcast that followed ordered Germans to stand

their ground against Allied armies or face enslavement.

A chilling message followed.

Any Germans, whatever his profession or class,

who puts himself at the service of the enemy

and collaborates with him will feel

the effect of a revenging hand.

A single motto remains for us, conquer or die.

- Adolf Hitler's stuck in this bunker,

never to emerge alive again.

And yet, it's rumored that werewolf operatives were sent

to this region to continue on.

- The notion that there were stray bands

of former SS roaming the countryside and terrorizing

the population obviously struck fear and horror in the minds

of residents and became part of the mythos of this area

that the Werewolves were fighting a rear guard action

to protect the secrets of the Third Reich

after the official end of the war in 1945.

- I've never seen the documents to say,

hey, go to the Owl Mountains and fight until

the end of the days.

But I think it's a reasonable assumption

that they were told that.

- In certain factions of the SS,

there were very fanatic members of that organization

who would have done just about anything

to protect the Third Reich that they so truly believed in.

- It kind of makes sense that the die hard Nazis

in the higher echelons thought that this would be

a logical place for one last hurrah.

- [Narrator] The Nazis furiously build this underground city

as their defeat looms.

- For all intents and purposes,

it was over the moment that

the Soviets broke out of Stalingrad.

- Surely, at that point in the war,

it would have been all hands to the pump

to be on the offensive at the front line.

- [Narrator] Closing in on Germany,

the Red Army pushes into the Owl Mountains,

only to discover a shocking network

of vast tunnels linked to even more mysterious structures

in the surrounding forest.

- It's really almost something truly out

of a science fiction movie.

- [Narrator] Not only was the complex itself sealed off

from the world, the fleeing Nazis made sure

to eradicate any documents left over pertaining

to its construction.

- There must've been a mass burning event

in the waning days of the war.

We know from other sites that that is indeed the case

and that Hitler was always telling his advisors when

they were moving from one place to another to burn papers

if they thought they wouldn't be coming back.

In the bunker, he's asking people to burn his papers

so that they won't fall into Soviet hands.

So one suspects that there was a concerted and probably

a sustained effort to burn all available evidence

about what the tunnels were used for,

a very deliberate policy under that scorched earth directive

to destroy information that could reveal the grand plans

for any installation or any particular location.

They would have had enough time, I think,

to get rid of quite a bit before

the Red Army actually arrived.

- [Narrator] Given the resources the Nazis had poured

into this complex up until

the final moments of the Third Reich,

modern day investigations have revealed sabotage entrances

and collapsed caverns.

What could have happened in the final moments

of the Osowka Complex?

- Some of them would have been destroyed

by the retreating Wehrmacht.

It appears the Soviets also blew up some of the tunnels

or the tunnels were blown up when they got there.

So there's a bit of a puzzlement

about what actually happened inside those tunnels

in the waning days of the war.

- Many people harbor all sorts of fantastical ideas

about what the Russians found in it.

- Because it was the Soviets who overran this area in 1945,

much of the information that they potentially uncovered

was taken back to the Soviet Union.

And because of the Cold War,

it was never disseminated in the West.

- [Narrator] Was it the Nazis who desperately needed

to bury the secrets of this complex?

Or did the Soviets discover something in the tunnels

and decide to prevent access to them forever?

- Visiting these Nazi bunkers and secret tunnels

is a chilling and haunting experience.

Many of them are in pristine condition.

You can almost feel, you can almost hear,

you can almost sense the Werhmacht,

the soldiers marching through.

It's unlike visiting other historic sites,

which you can appreciate the history,

you can appreciate the architecture.

But when visiting any Nazi site,

one is reminded of the evil that was happening

at that facility.

- But the fact that we can't see,

or haven't discovered the real extent of this system,

that's the biggest mystery.

What else is under there?

What might we find if we're able to explore deeper?

- All kinds of new stuff continues to come to light,

even things as simple as diaries that soldiers

on the Eastern front wrote, but also,

important papers that were not destroyed in time.

And that's why we have these stray pieces

and the job of scholars and historians,

their job is to put all of these little bits and pieces

into some kind of coherent narrative

that may help us make broader sense

of a project of this scale.

- The reality is is that there are many,

many more stories that we're still questioning.

And we probably will for a very long period of time.

- Truth is layered, but by combing the archives,

and putting together evidence in a responsible way,

we can approximate a truth of what the plans

for that set of structures.

- We know much, much more than we knew 50 years ago,

but we can only imagine the final view and the dimension

of all those complexes if that will be finished.

- [Narrator] Evidence mounts, suggesting the Osowka tunnel

was simply one part of a much larger super complex

throughout the Owl Mountains.

And continued investigations promise

to uncover new secrets locked in the walls

of this underground city.

[dramatic music]