Planet Appetite: Going Underground in Europe's Largest Cave, Postojna, Slovenia

In Postojna Cave, Slovenia, anyone can take a train and explore 5 km of underground tunnels and passages, or you can sign up for an adrenaline adventure tour and taste the real caving experience.

It's Friday night, around midnight, I'm deep underground inside Postojna Cave, the guides have told us to find our own way out, and I'm beginning to panic. We're retracing our steps from deep inside the cave, where we've come to a dead end and can't go any further, and now seem on the road to nowhere. It's been tough going, clambering over boulders, wading through water, sliding on muddy rocks, always careful not to grab the stalagmites lining our path for balance. After all they've been here for hundreds of thousands of years, and it wouldn't do to damage them.

There's a disagreement about the correct way out and we splinter into two groups. I press on, convinced I'm right, and after about half an hour manage to get back on track and find the path. The others who take a different direction eventually arrive, slightly shaken, but exhilarated - they've had to squeeze through the narrowest of passages, filled with water, and are completely soaked, but glad to be out.

Of course you don't have to do this - this is the adrenaline adventure tour and we're suited up in protective overalls, equipped with acetylene lamps, and determined to experience the real underground experience. Most of the cave's yearly million visitors enjoy a leisurely 2 km underground train ride and then take a guided walking tour, lasting about 90 minutes, without special clothing. An illuminated pathway takes them over the Great Mountain (the Cavalry), across the Russian Bridge, then into the Beautiful Caves, consisting of the Spaghetti Hall, the White Hall and the Red Hall. They're named after the characteristic colour and shape of their stalactites and stalagmites.

Finally you reach the Brilliant, the most famous stalagmite in the cave, standing almost 5 metres. It's still growing, as there's a strong and even drip from the ceiling, depositing a thin layer of calcite sinter on the rounded crown of the stalagmite. The drips build other stalagmites, wall linings, pools, crusts and other fantastic forms in the cave. The walls of the hall flaunt sinter curtains, there's a sinter fountain called the Organ and tiny stalactites hang from the ceiling. This is one of the most beautiful spots in the cave.

Although people have lived near the cave's entrance since prehistoric times, it was only in 1818 that Luka Čeč discovered a previously unknown passage during preparations for the arrival of the Austrian Emperor. Crown Prince Ferdinand was the first tourist to walk through the newly discovered part of the cave and the rest, as they say, is history. In 1857 Emperor Franz Joseph and Empress Elizabeth made an official visit and the cave was lit with over 12,000 candles and flaming torches, 1500 of them in the Great Hall alone. The cave railway was opened in 1872 with over 2 km of tracks - in those days the guides pushed the cars by hand, but petrol locomotives were introduced in 1924. Today the line is double tracked, to reduce bottlenecks, and there's a total of 3.7 km of rails.

The Postojna Cave also provides shelter to more than 150 animal species and visitors can get to know some of the most interesting ones in the Vivarium Proteus, just by the entrance. There's a mixture of midget spiders, beetles, water lice, grasshoppers, shrimps and water snails all adapted to life underground, but the strangest is the Proteus or human fish. At 25 to 30 centimetres in length, it's the largest cave-dwelling animal and is the only vertebrate in Europe that lives solely in the subterranean world. It used to be believed that they were tiny dragons that lived underground and, at one time, they were a local delicacy. These days they're protected and are only found in Slovenia, Bosnia and Herzegovina and Croatia.

Predjama Castle

The cave is not the only attraction in this part of the world. Nearby is the magnificent Predjama Castle, hollowed into the hillside, clinging to a vertical 123 m cliff, with caves below and behind. The River Lokva disappears into the underground world deep down below the castle and there are secret passages which allowed the inhabitants to escape to the world above. The cave system below is the 2nd largest in Slovenia and has over 25 km of tunnels. At this time of the year it's populated by bats and I'm not allowed in to disturb them.

Lipica Stud Farm

Around 40 km away is the Lipica Stud Farm where the famous Lipizzaner horses have been bred for over 400 years. The soil and climate of the area is very similar to that of Spain which is why the Hapsburg Archduke Charles chose to build the royal stud farm here in 1578. They supplied horses to the Spanish Riding School in Vienna until the Hapsburg Empire met its end in WW1. These days they have over 300 horses and stage equestrian displays in the summer. You can also take carriage rides round the estate, and ride the horses after a few lessons.

Ljubljana

Slovenia's tiny capital is well worth a visit and the city centre is completely pedestrianized. It was largely rebuilt after a terrible earthquake in 1895 and shows a surprising unity of styles, largely due to architect Jože Plečnik. He renovated the city's bridges and the Ljubljanica River banks, as well as designing the university library and numerous churches. The castle, accessed by a brand new funicular, houses the excellent Restaurant Na Gradu which is well worth a detour.

Wizz Air and EasyJet fly direct to Ljubljana from London. Additionally Trieste, Zagreb, Pula and Rijeka airports are close by, giving a greater range of options.