Eastern Europe is a wild and dramatic place,
a territory of craggy mountains and harsh terrain.
Deep in its remote heart
lies a forbidding and impregnable structure,
the largest cave castle in the world.
It's called Predjama,
and its intimidating walls and stunning backdrop
hide life-and-death stories of struggle and survival.
Here, in the Middle Ages,
a renegade knight -caught between empires-
sought safety behind its walls.
Animals, too, vie for protection in its shadow.
But this place is not for the weak.
These mountains are filled with danger and deception...
Porous rocks spew raging torrents...
Lakes come and go like ghostly apparitions...
And bizarre creatures lurk in the shadows.
This is the story of Predjama.
The Predjama cave castle lies in what is today Slovenia,
south of the Austrian Alps and east of Northern Italy.
The landscape is epic and powerful.
It's known as the Karst -limestone mountains
with steep, water-carved canyons riddled with caves.
It's also filled with life.
All manner of wild beasts roam these forests.
Historically, the 267-square mile
Karst region was known mostly
for the port of Trieste on the Adriatic Sea,
where salt from the region
was shipped across the Mediterranean.
In the late 15th century, two superpowers,
the Austrian Habsburgs and the Kingdom of Hungary,
were vying for control of the port
and the surrounding plateau.
But it was a single individual -a notorious knight-
who gave rise to the legend that has come to define the Karst.
His name was Erasmus Leuger,
a Habsburg nobleman
living in the great Habsburg city of Vienna.
In the fall of 1483,
Erasmus killed another nobleman to defend a friend's honor,
then fled into the Karst to avoid death himself.
He had a particular hideaway in mind.
His family owned the remote mountain fortress of Predjama.
Built in the 12th century,
the castle sat in the mouth of a mountain cave,
and had been owned by other noblemen before Erasmus.
But the cave's history of human occupation
starts eons before that.
As long ago as the Stone Age,
its caverns had offered people protection.
It seemed like a perfect hideaway
for an outlaw like Erasmus,
though others might have been fearful
of evil omens in the air.
Ravens, thought of in medieval times as heralds of doom,
also call the castle home.
Despite their shady reputation as scavengers,
these birds are actually excellent providers,
using cleverness and cunning to raise their young.
Like Erasmus, the ravens use the steep cliff walls
of the Karst for protection.
The precarious perch keeps the chicks safe as the adults hunt.
(Chicks chirp)
NARRATOR: Both parents care for the three-week-old chicks.
In order to fill five hungry stomachs,
they have to fly several miles a day
in search of carrion, insects and bird eggs.
Common ravens have excellent eyesight,
helpful for spotting prey or carcasses from the air.
They both hunt and scavenge,
anything to keep the young chicks fed.
The ravens aren't the only ones looking for a meal.
Wild boars roam these woods,
and were no doubt hunted by Erasmus in his day.
They're omnivores, and use their snouts
to dig up tasty grubs.
A clever bird takes notice.
His loud caws alert his pals.
They gather for the feast.
(Boar grunts)
(Boars grunt)
NARRATOR: The boars can be intimidating,
but these insects are too nutritious to pass up
on account of aggressive swine.
The ravens work together to keep them at bay.
They're careful, but refuse to be chased off.
(Ravens squawk)
NARRATOR: Left alone in the nest,
the raven chicks are getting ready to fledge.
Without parental supervision, they're taking dangerous risks
as they stretch their wings.
On these high cliffs, one wrong move could be fatal.
(Ravens caw)
NARRATOR: The first to take flight
is rewarded with a snack from her returning dad.
(Ravens caw)
(Chicks chirp)
NARRATOR: Perhaps spurred on by their sister,
the other siblings gingerly emerge,
eager for freedom and ready to soar.
(Ravens caw)
(♪♪♪)
NARRATOR: As the young ravens take flight,
they get their first aerial view
of the rugged mountains they'll call home.
It won't take them long to master their domain.
Ravens are considered
one of the most intelligent species of bird.
Their wisdom and wings will serve them well
as they navigate the sheer outcrops and jagged rocks.
For the earthbound inhabitants of the Karst,
getting around is a more challenging endeavor.
Specialized climbing gear is often a requirement.
The chamois, a relative of goats and sheep,
has just the hardware.
Its pliable but sharp-edged hooves
allow it to find purchase on seemingly impossible terrain.
It navigates the rocky outcrops with balance and agility
and can leap 6 feet straight up in a single bound.
In medieval times,
the chamois was hunted for its meat,
and its horns were used to make
a musical instrument called a gemshorn.
Hunters would stalk it from above,
because it habitually looked downhill for danger.
The chamois spend months at a time
foraging in these mountains.
Only when the weather gets cold and the food becomes scarce
will they leave for the more protected valleys below.
(♪♪♪)
NARRATOR: In 1483, just as the chamois would have been
heading down the mountain for the winter,
Erasmus Leuger was heading up.
An outlaw after killing a fellow nobleman in Vienna,
he was fleeing to the safety of Predjama castle.
He wasn't a moment too soon.
Winter was settling in,
and travel in these parts can be deadly in the cold.
Temperatures drop to -30° Fahrenheit
and deep snow makes the terrain all but impassable.
When Erasmus looked up at the imposing ramparts
of his family's castle, he knew he'd be safe.
(♪♪♪)
NARRATOR: Unlike many other European castles,
Predjama has never been luxurious.
Its Spartan walls have been built up over the centuries,
but it was always more of a fortress than a palace.
One of its few indulgences was a private outhouse
with a spectacular view of the valley below.
But the castle's most impressive feature
was its seamless connection with the hidden caves behind it,
which extend deep into the mountains.
Predjama would have looked
like little more than a dungeon to Erasmus.
An uncomfortable hiding place for a Habsburg aristocrat
used to the extravagances of cosmopolitan Vienna.
But faced with the death penalty,
Erasmus was in no position to complain.
Winter was closing in.
With only his faith and a few servants
for support and companionship,
he holed up behind the castle walls like a rodent.
Erasmus wasn't the only one seeking shelter here...
The dormouse also spends winters in the castle,
though it's a quiet housemate.
It hibernates through the coldest months,
slowing its metabolic rate
and lowering its body temperature dramatically.
All in an effort to use as little energy as possible.
Fat supplies from the previous summer
can sustain it for up to six months or more.
Behind the castle,
5 miles of twisting tunnels
and hidden chambers provide sanctuary
for more bizarre creatures,
which thrive in the moist interior.
The cave cricket is happiest in absolute darkness.
Although it has big eyes, they've been rendered useless
by generations of living in the dark.
The cricket is completely blind.
It relies on its long sensitive antennae
and sense of touch to get around,
seeking out fungi and other organic debris for food.
The crickets scurry about on the rocks,
but many of the cave's other occupants are aquatic,
lurking in the pools and waterways
that meander through the tunnels.
One strange beast that haunts these waters
is the mythical olm,
a seldom-seen, entirely aquatic salamander.
Nicknamed "the human fish" because of its pale skin,
it has both gills and functioning lungs,
can grow to almost 1.5 feet long,
and can live up to 100 years.
Olms feed on shrimp and other tiny aquatic animals,
which they find using a sensitive lining in their ears
that detect even the smallest vibrations in the water.
Their keen sense of smell and taste
also help them navigate in the dark.
But olms don't need to eat often.
When food is scarce, they slow their metabolism,
and have been known to survive up to 10 years on a single meal.
As the largest creature in these caves,
the olm has only one natural enemy...
...daylight.
Leaving the cave would literally burn
its photosensitive skin.
Erasmus could at least see sunlight,
but he too was confined to the caves and the castle.
Fearing discovery,
he was forced to rely on his servants for supplies.
Out here in the winter wilderness,
there was plenty of game for hunting.
But the servants weren't the only ones looking for meat.
The lynx is the largest cat in Europe,
and a versatile predator.
The alpine hair is one of its favorite meals.
(♪♪♪)
NARRATOR: The lynx can accelerate to over 40 miles per hour
for short bursts, but today he's out-maneuvered,
perhaps distracted from the bunny by meatier prey.
He could feed on this doe for several days.
But she's not alone,
and he'd have a hard time separating her from the herd.
Before he has time to reassess,
the lynx is distracted once again
by something even more attractive than food,
the scent of a female in heat.
Late winter is mating season for the lynx.
They're normally loners, but at this time of year,
males and females seek each other out before the thaw.
The female will only mate with a single male per season,
so he must convince her he's worthy.
(Female lynx snarls)
NARRATOR: Eventually, she deems him adequate,
and he quickly moves in before she changes her mind.
The kittens will be born in about ten weeks,
but by then, their father will be long gone.
The snow will be too,
giving way to the flowers and flourish of spring.
Here in the Karst, spring also unleashes
powerful forces that liquefy the landscape.
Mysterious upwellings appear out of nowhere.
Water gushes where previously there was none.
Dry walls of rock suddenly bleed waterfalls,
and raging rivers emerge from dry earth.
(Birds sing)
NARRATOR: Within days, the floods create a completely new habitat.
(Bird sings)
NARRATOR: Not far behind come the creatures who exploit it.
One of the first arrivals is the white-throated dipper,
an energetic bird that is more at home in the water
than in the air.
Undeterred by the strong currents,
he wades into the river in search of caddisfly larvae.
(Bird sings)
NARRATOR: At this time of year, the larvae aren't for him.
He's bringing them back to his chicks,
tucked safely away inside a nest in the rocks.
(♪♪♪)
NARRATOR: Both parents help feed the young,
fattening them up as quickly as possible.
It won't be long before they'll have to leave the nest,
and face the unbridled force of the river by themselves.
(♪♪♪)
NARRATOR: Meanwhile, the water levels continue to rise,
filling the ravines and saturating the land.
The rivers follow courses carved into the limestone
over millions of years.
Naturally acidic rainwater dissolves the porous rock,
leaving the Karst riddled with caves and tunnels
that channel the runoff downhill.
In spring when the snow melts, the added volume
flushes the labyrinths and floods the landscape.
Sometimes it carries with it the denizens of the dark.
For centuries, most people only saw olms
when they were washed from the caves.
They thought the bizarre salamanders
were actually baby dragons,
torn from their mothers by the raging water.
And that the angry dragons inside
were the ones causing the floods.
(♪♪♪)
(Birds chirp)
NARRATOR: Back on higher ground,
the dipper chicks have left the nest.
The five youngsters have set out to explore,
braving the rushing water in search of a meal.
They bob as they move,
either as a means of communication
or to throw off predators eyeing them from above.
They're immediately comfortable on the slippery rocks,
but still tentative about going for a dip.
They spend the first couple of days
figuring out what's edible and what's not.
And they're not above calling for help
when they get into trouble.
Fortunately, they're not yet entirely unattended.
A few loud alarm calls and help arrives.
(Birds chirp)
NARRATOR: For the next few weeks, their parents will continue
to watch over them.
After that, they'll be on their own,
and they'll need to be completely at ease in the water.
Dippers wade into the current, picking insects off the rocks.
But they also fully submerge in search of shrimp and small fish,
using their wings to swim.
They're perfectly equipped for the spring runoff
that washes through the Karst.
As spring unfurled around him,
Erasmus, the outlaw knight,
remained cooped up in his cliff-side fortress.
But his food stockpiles were running low,
partially eaten by some unwelcome houseguests
who were stirring after months of deep slumber.
The dormice were famished,
and the knight's food was a perfect amuse-bouche.
Fortunately for Erasmus,
the mice are inclined to eat and run.
There are fresher offerings outside.
(♪♪♪)
(Bird sings)
NARRATOR: With their bushy tails,
dormice resemble small squirrels,
and similarly head to the forest in search of nuts.
Beech nuts, hazelnuts, acorns...
they'll gorge on everything they can find.
After a winter of hibernation,
they need to replenish their fat stores,
and these oily fruits are just what they crave.
First, they'll regain their strength,
then they'll reproduce.
Out of money and unable to pay his servants
to keep him fed and safe any longer,
Erasmus was forced to leave the castle as well.
Still wanted by the Habsburg court,
he decided to turn against them.
He offered himself up as a mercenary
to the enemy Hungarians.
He was adding treason to murder, but he had little choice.
The main battles between the Habsburgs and the Hungarians
were for control of the Mediterranean port of Trieste.
But Erasmus was given a different objective.
The Hungarians tasked him
with wreaking havoc in the countryside,
working alone to attack wealthy Habsburg estates and villages.
To some he was a Robin Hood figure,
provoking and stealing from the rich.
(Bear growls)
NARRATOR: But to others, he was no more honorable
than the marauding brown bears that occupy the Karst.
The bears are dangerous opportunists,
they'll hunt, scavenge and forage to survive.
And like Erasmus and the Habsburgs,
they'll also attack their own kind.
In spring, female bears roam the Karst
accompanied by young cubs.
They're fiercely protective,
especially when faced with a male
that would readily kill the cubs
to bring the female back into estrus.
The male weighs his odds.
The young cubs are oblivious to the danger,
but their mother goes on the offensive,
instead of waiting for an attack.
(Bear roars)
NARRATOR: The male is not up for the fight.
With the threat gone, the young bears devote themselves
completely to play.
(♪♪♪)
(Bear growls)
NARRATOR: They're learning how to get around in the Karst,
growing stronger and more confident as they explore.
Their mother stays close,
teaching them what being a bear is all about.
(♪♪♪)
NARRATOR: By the time they're two, they'll be on their own.
But for now, they're safe under their mother's watchful eye.
Below the mountains at the edge of the forest,
a stunning transformation is taking place.
The grassy valley is turning
into a massive but temporary seasonal lake.
Where there was once dry earth,
there is now water and fish.
In Erasmus's time,
some credited witches and sprites
for making them magically appear.
Today we know better.
The fish arrive through underground channels
in the porous Karst.
The lake, called Cerknica,
also attracts all manner of birds.
Resident species, like the grey heron,
touch down as soon as it fills.
Migrants come too.
Redshanks...
Wild ducks...
Lapwings...
...and wild geese
all use the lake as a convenient rest stop.
And just like at Predjama,
animals find shelter in its secret retreats.
Hidden in one of the lakeshore caves,
several thousand grass frogs
have been waiting out the winter.
They can't reproduce until the water arrives.
To mate, the male climbs onto the female's back
and hangs on for the journey to the lake.
(Insects chirp)
NARRATOR: Here, they spawn a new generation.
In two weeks, the fertilized eggs hatch
into vigorous tadpoles.
The lake provides sustenance, but has its threats as well.
The larva of the great diving beetle seems innocuous...
...but its lethality should not be underestimated.
It's equipped with powerful jaws for gripping much larger prey.
The beetle follows its initial assault
with the injection of corrosive digestive juices
into the still-struggling victim.
The poison paralyzes the tadpole
and dissolves it from within.
Then, the larva sucks out the predigested mash
through a canal in its jaws.
Such gruesome death is a way of life in the Karst.
A powerful reminder of the high stakes of survival.
As Erasmus continued his plunder,
he believed he was one of the hunters.
But on one of his raids,
he was spotted by Habsburg soldiers.
When he tried to escape,
they followed him back to Predjama.
He barely made it to the safety of the castle,
where his pursuers were helpless
against the vertical rock and overhanging ramparts.
All they could do was stare up into the heights,
longing for the talents of the acrobatic wall creeper.
(Bird calls)
NARRATOR: This flashy bird is not much of a flyer,
but it uses its stubby wings and sharp claws
to bounce and climb on the smooth rock walls.
(Birds chirp)
NARRATOR: Lacking the wall creeper's athleticism,
the Habsburg soldiers opted for a more sedentary approach.
They laid siege to the castle,
determined to outlast the outlaw and bring him to justice.
Trapped, Erasmus withdrew into the castle once again,
alongside its more permanent residents.
In his medieval world,
he would have recognized these castle-mates
as harbingers of doom.
A colony of bats hibernates quietly in the caves
during the cold Karst winter.
But in late spring they're awake and hungry.
These are common bent-wing bats,
which thrive on moths and flies that they capture on the wing.
But in the Middle Ages,
people here believed bats pursued human prey,
turning them into the infamous undead.
This region is where
the original vampire myths come from.
The first reports of such horrors
came from the town of Kringa,
only about 60 miles to the south.
According to legend, a dead farmer in this cemetery
left his grave each night to terrorize the town.
The priest and villagers tried to kill the vampire
with crosses and stakes.
But it wasn't until they cut off the corpse's head
that the nightmare finally came to an end.
(Owl hoots)
NARRATOR: Erasmus was no vampire,
but he was still trapped in the castle
by the posse of Habsburgs.
While he was holed up, other residents of the Karst
were enjoying the bounty of summer.
The lake below the castle is a favorite breeding ground
for the magnificent great crested grebe.
These water birds have legs placed far back on their bodies.
This makes them excellent swimmers,
but rather unstable on land.
During mating season,
the birds engage in an elaborate courtship.
The male poses,
and proudly shows off his prowess as a diver.
The two synchronize movements...
...then, finally, elevate together
into the triumphant "penguin display" ballet.
On the shores of the lake,
a more sinister seduction takes place.
Drosera, commonly known as sundew plants,
are carnivorous, the tentacles on their leaves
are covered with sweet, sticky droplets
that are irresistible to insects.
But when the insects alight,
they find themselves caught in a trap.
Just like Erasmus, trapped in his castle.
But unlike the insects,
Erasmus's fate wasn't yet sealed.
He still had a trick up his sleeve.
Sneaking through a secret tunnel
that snaked from the castle through the cave system,
he headed off to an unwatched valley
on the other side of the mountain.
(Dripping water)
NARRATOR: He could have escaped completely this way,
but was confident he could outlast the soldiers,
and chose to stay in his family castle.
(♪♪♪)
NARRATOR: Here in the valley, he could roam free...
...and pick fresh fruit from the ripening trees.
Like Erasmus emerging from his cave
to taste the sweet nectar of freedom,
mayflies burst from the lake every summer.
They spend most of their lives as nymphs in the water,
but their final molt gives them wings.
The adults rise up into the sky en masse...
...with only one goal, to reproduce.
In massive throngs, the males fly across the lake.
Females join the so-called wedding swarms,
and they mate in flight.
(♪♪♪)
NARRATOR: But their airborne freedom is short lived.
Exhausted from the effort,
they fall back into the water from whence they came.
With their dying breaths,
the females lay their fertilized eggs
into the clear, still water.
Erasmus didn't know it,
but his last breath was fast approaching as well.
He was still enjoying his freedom,
out in the fruitful Vipava valley.
Here in the sun, just a few miles
from the castle, grapes and cherries ripen weeks earlier
than in the shadow of Predjama.
Others descend on the valley for the seasonal bounty as well.
Finished with his early season nuts,
the dormouse is filling up on sugar-rich fruit.
(♪♪♪)
NARRATOR: He's so focused on his meal,
he's oblivious to a dangerous predator lurking nearby.
Finally satisfied,
the dormouse heads back towards the safety of his burrow.
But the Ural owl,
one of the largest in Europe with a wingspan of up to
4 and a half feet, has him in her sites.
She swoops in on silent wings.
Up in the trees,
her owlet waits impatiently for a meal.
It's survival of the fittest out here in the Karst.
Death for the dormouse means life for the owl's hungry chick.
He's only recently left the nest,
still strengthening his wings before taking to the air.
His mother offers him the entire dormouse,
wanting him to get used to eating whole prey.
He's not quite sold on all the fur and bones.
Eventually he nibbles,
but mom will end up eating most of this meal.
Over the next few days,
the owlet practices his flapping.
He's building up
to the takeoff and the freedom of flight.
Fresh fruit in hand,
Erasmus returned to the castle
through the secret tunnel underneath.
He even brought cherries for the soldiers,
to show them their siege was a farce.
But the soldiers were ready for his games.
When one of his servants brought them the cherries,
they convinced him to turn on his master.
It probably took little more than some money changing hands.
The servant would send a signal
when Erasmus was on the toilet,
the only spot in the castle that was vulnerable from below.
The soldiers had brought along a catapult
for just such a mission.
They prepped for the attack,
then settled in to wait for their cue.
They weren't the only ones in the Karst
who favor an ambush.
Among the rocks and crevices,
a horned viper sets its own trap,
flashing its red tail
to attract the attention of an unsuspecting mouse.
But just in time, the mouse smells a rat.
The viper changes tactics and gives chase.
The mouse tries to hide in the rocks.
But the snake patiently follows.
Timing is everything.
The snake has a well-earned meal.
The calories will keep him full for weeks.
For months, Lake Cerknica has been a rich oasis
for all kinds of fish and fowl.
But in late summer,
when the meltwater from above finally wanes,
the lake dries up and disappears
almost as fast as it grew in the spring.
Some water evaporates into the dry mountain air.
The rest seeps back into the invisible warren of channels
that riddle the Karst.
Once again, the change offers opportunity for some
and danger for others.
Some fish become trapped by the receding waters,
easy pickings for resourceful hunters.
(Raven caws)
NARRATOR: Back at the castle,
the pursuers were circling Erasmus as well.
The Habsburg soldiers, eager to end the siege
before the onset of another harsh winter,
finally got the signal
from the traitorous servant behind the walls.
Knowing they'd only have one shot,
the soldiers took careful aim...
...and released the projectile.
(Rock booms)
NARRATOR: It was a perfect strike.
Seated in the outhouse,
Erasmus met his end astride a throne
that was anything but royal.
Centuries later,
the story of the outlaw knight has faded into local lore.
Some still revere him for his loyalty to his friend
and his Robin Hood-like stand
against the evil Habsburg Empire.
Others revile him as a coldblooded killer
and a traitor to boot.
The details of Erasmus's exploits have blurred with time,
but his spectacular castle
still casts a long and powerful shadow.
Out here on the edge of nowhere,
where hollow mountains hide mysterious beasts,
where water bleeds from porous earth...
...and where powerful forces spur legends and myths...
...the life-and-death struggles
of hunter and hunted continue eternally...
...as the cave castle stands watch.
(♪♪♪)