Europe's largest show cave is home to about 100 different animals which never leave and live in darkness

Most popular formation is a 16-ft tall stalagmite known as 'The Brilliant', which is an estimated 100,000 years old

Postojna Cave contains incredible layers of detail and cavernous galleries decorated with ancient formations


‘Whatever you do, be careful not to touch them.’

Our veteran guide’s warning is very clear as we set off to explore Europe’s most popular show cave in a way that very few tourists have before.

With the light from his head torch cutting through the darkness in front of us, he’s referring to the endless number of ancient stalagmites that rise from the floor of western Slovenia’s spectacular Postojna Cave.

Oil from a human’s skin can disrupt the growth of the stunning limestone formations, and our guide’s warning underscores how precious they are and how important it is to preserve them.

Full disclosure: I had no choice but to grab onto a couple of them as I struggled to maintain my balance while trekking through the cave during a challenging adventure tour offered by its operators.

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Postojna Cave's adventure tour allows visitors to explore its magnificent tunnels, caverns and galleries without barriers

It’s late on a Friday night and everyone in my group is dressed in mud-spattered coveralls and wellies, while alternating between battery-powered and carbide torches affixed to our helmets.

I tiptoe around the stalagmites as if they were landmines, and between every step I pause to marvel at my surroundings – Postojna Cave has incredible layers of detail and cavernous galleries that make its visitors feel incredibly small.

It has taken tens of thousands of years for every scar to develop into a magnificent stalagmite, stalactite, column or curtain – one drop of water at a time.

The last thing I want to do is stunt their growth as I cautiously crawl under low ceilings and through narrow tunnels, and climb and descend rugged hills inside the cave, which was carved by the Pivka River.

For a greater challenge, visitors who opt for the adventure tour can test their endurance and climbing skills with a number of challenges

Oil from a human’s skin can disrupt the growth of the stunning limestone formations known as stalagmites and stalactites

An experienced tour guide explains the cave system to a group of visitors before embarking on the adventure tour

Deep inside the cave, at a depth of nearly 500ft, we extinguish our carbide torches and stand in complete darkness to absorb the cave's natural sounds.

It was an eerie yet peaceful experiment as the silence was intermittently broken by the sound of water droplets hitting the floor – an underground symphony that has existed for millions of years.

Moments later, I’m standing in awe of ‘The Brilliant’, a 100,000-year-old, gleaming white stalagmite that glistens against the glow of my carbide torch.

This fascinating formation is 16ft tall, and has the appearance of a stack of marshmallows which have been melted and sprinkled it with sugar.

Postojna Cave's most popular formation is a 16-ft tall stalagmite known as 'The Brilliant', which is an estimated 100,000 years old

Entering Postojna Cave in western Slovenia, approximately 31 miles from the capital, Ljubljana, is like stepping into an alien world

Postojna Cave has incredible layers of detail and cavernous galleries that make visitors, which number in the thousands, feel incredibly small

There doesn't appear to be a smooth surface in sight - other than the walkway - in a cave decorated with millions of jagged formations

STALAGMITES, STALACTITES AND CURTAINS DEFINED Stalagmites: These formations rise from the floor of a cave thanks to constant drips of water containing mineral deposits. Most have round or flattened tips. Inside Postojna Cave, the most magnificent of them all is the 16-ft tall ‘Brilliant’, a gleaming white formation with a thin layer of pure calcite sinter. Stalactites: These icicle-shaped formations with pointed tips hang from the ceiling of a cave. They are produced as water containing mineral deposits drips through a cave’s ceiling. Stalagmites and stalactites form a pillar when they meet. Curtains or draperies: These spectacular formations form when water trickles down the roof or wall of a cave. The sheets of calcite take a wavy shape, just like folded curtains or draperies. They hang downward and tend to be very thin, but solid. Source: NOAA This fascinating curtain, reflecting in artificial light, formed as water trickled down the roof and wall of Postojna Cave Advertisement

It was just as magnificent when I revisited it the following day as my group took part in the cave's normal 90-minute walking tour that is taken by more than half a million visitors a year.

With almost 14 miles of passages, Postojna Cave is one of the world’s largest karst monuments and one of the richest for limestone formations.

To reach its depths, visitors are taken on a fun train ride on a mile-long track. It is the only cave with a double track railway.

From the moment the train departs, it is like stepping into an alien world. White and rusty red stalagmites and stalactites twinkle in the light along the illuminated track, which leads to the main tourist section, and the network of tunnels and caverns seems to go on forever.

To reach the depths of the cave, visitors are taken on a fun train ride on a mile-long track. It is the only cave with a double track railway

Visitors admire stalactites, stalagmites and pillars in a gallery known as the white hall due to the colour of the formations

This gallery, known as spaghetti hall, features thousands of string like stalactites which hang from the ceiling

The ancient Postojna Cave was carved by the Pivka River, which runs above and below ground for nearly 18 miles

POSTOJNA CAVE'S MOST FAMOUS RESIDENT Postojna Cave is home to about 100 different animals who never leave and live in complete darkness. None are more famous or celebrated as the unusual olm (Proteus anguinus), a blind amphibian which has become a symbol of the cave. It is known by many names, including cave salamander, baby dragon and human fish. With a maximum length of about 11 inches, there are thousands of the creatures within Postojna Cave, and they were first described by visitors in 1768. They can live up to 100 years and are neotenic, meaning adults keep most of their juvenile features. Aside from human fish, the cave is home to tiny spiders, tiny-neck beetles, water louses and grasshoppers. Visitors can explore Vivarium Proteus, which shows off some of the creatures found within the cave. Postojna Cave's most famous resident is the olm, also known as the cave salamander, baby dragon and human fish Advertisement

There are very few smooth surfaces – jagged stalactites descend like they were driven through the ceiling, while curved stalagmites appear as though they were moulded by the careful hands of artisans.

Visitors on the normal tour – available in 15 languages – have access to about three miles of the cave, including a smooth, half-mile walkway that is wheelchair accessible (it has no steps but there are some steep inclines).

The temperature inside the cave is constant year-round at just under 10 C, meaning most visitors will feel comfortable in a jacket, trousers and trainers.

Postojna Cave has been a tourist attraction for almost 200 years since its deeper sections were discovered by Luka Cec, a local man, and it was used by German forces to store aircraft fuel during the Second World War.

Part of the cave was ruined when the fuel was destroyed by partisans, sparking a massive fire that burned for days.

Preseren Square, where three bridges cross the Ljubljanica river, is an extremely busy meeting point in the heart of Ljubljana

Three days in Slovenia

After emerging from the cave, I spent my second night touring Slovenia's charming little capital, Ljubljana (pronounced Loob-liana), just 30 minutes north-east of Postojna.

With the Ljubljanica river cutting through its lively centre, it lives up to its reputation as one of Europe's cleanest and prettiest capitals.

Our guided tour straddled both sides of the river as we passed couples enjoying dinner on restaurant terraces, young friends sharing laughs over drinks, and a mother encouraging her young daughter to dance as a man played traditional songs on the accordion at Preseren Square.

It’s an extremely busy meeting point on this Saturday night in a city that traces its roots to an ancient walled Roman city.

Other stops on our tour included the odd-looking National and University Library of Slovenia, Congress Square, Ljubljana Town Hall and Ljubljana Castle, which has been transformed into a modern and hip gathering place with restaurants, cafes and a nightclub.

Just six miles from Postojna, Predjama Castle is built in the gaping mouth of a cave in the middle of a 400ft rocky cliff

The castle was referred to in writing for the first time in 1202 and holds a Guinness World Record as the largest cave castle in the world

Predjama Castle offered little comfort for its residents, but it has sweeping views of a valley and the village of Predjama

On my final day in Slovenia I visited the marvellous Predjama Castle, just six miles from Postojna.

This is the beauty of Slovenia. It has a lot to offer and is a small country, meaning tourists can cover a lot of ground in just a few days.

Predjama Castle, meanwhile, is an incredible sight from the outside – a medieval structure built in the gaping mouth of a cave in the middle of a 400ft rocky cliff, providing ultimate protection from enemies.

Inside, it offered little comfort for its inhabitants in times of peace and conflict.

In addition to castle tours, visitors can explore part of a cave that is located underneath it and open from May to September.

Where to eat

Proteus Restaurant: Located next to Postojna Cave Rooms & Apartments Proteus, this restaurant is a short drive from the cave. It offers traditional Slovenian dishes – hearty comfort food – with a contemporary twist and local wines. Examples include house-made pumpkin soup with foam made from pumpkin seed oil, dry-cured ham terrine, and delicious venison.

Jamski Dvorec Mansion: This is a convenient stop for cave visitors, as it is just steps from the entrance. It blends regional, hearty meals with modern trends. The menu includes everything from octopus salad and stuffed veal rolls to traditional goulash or local game.

Gostilna na Gradu: This cosy restaurant in Ljubljana Castle sources local ingredients to serve up mouth-watering traditional dishes such as roasted deer and pork tenderloin stuffed with cheese and spinach fried in almonds. Even the schnapps is made from flowers from the karst region.