Postojna Cave: Slovenia’s Most-Visited Cave, Explained

The cave sits in the heart of Slovenia’s karst, part of the same limestone belt covered in our guide to Slovenian caves and karst. The Pivka River still carves the lower levels today, and the route open to visitors includes some of the largest decorated chambers open to the public anywhere in Europe.

Here is what to know before you go, and how it compares to Skocjan, the other cave people ask about.

Postojna Cave at a Glance

• First discovered13th century (signatures dated 1213)
• Opened to visitors1819
• Total explored lengthAbout 24.3 km
• Open to visitorsAbout 5 km (3.7 km by train, rest on foot)
• Deepest point115 m below the entrance
• Underground railwayRunning since 1872
• Temperature insideAround 10°C year-round
• Annual visitorsSeveral hundred thousand
• Formed byThe Pivka River, over roughly 3 million years

A Short History of Postojna Cave

People knew about Postojna long before anyone thought to sell tickets. Signatures scratched into the walls date back to 1213, left by visitors who reached only the first, cramped chambers near the entrance.

Everything changed in April 1818, when Luka Cec, a local man employed to light lamps ahead of a royal visit, wandered past the point earlier visitors had reached and found the vast decorated galleries that make up today’s route — by his own account, he described it as a paradise. The cave opened for organised visits the following year, in 1819, after a visit by Archduke Ferdinand I, making it one of the earliest show caves anywhere.

In 1872, rails were laid through the horizontal passages for the world’s first railway inside a cave — at first pushed by hand, later pulled by gas and then electric locomotives. Electric lighting followed in 1884, reportedly before the streets of Ljubljana or London had it. The passages open today have grown since: an older survey put the explored system at around 20.6 km, extended through further exploration to today’s roughly 24.3 km.

What the Tour Is Actually Like

Every tour starts with a train ride: about 3.7 km on the world’s only double-track cave railway, through narrow passages that open suddenly into chambers several storeys high. From there, groups continue on foot — roughly 1.5 km along a paved, gently sloping path — with a guide in your own language for the busiest slots and shared multilingual commentary at quieter times. The whole tour runs about 90 minutes.

Photography is allowed throughout, unlike at Skocjan. Two things catch first-timers off guard: the temperature, a constant 10°C even in the middle of summer, and Brilliant, a five-metre pure-white stalagmite that has become the symbol of the cave. The walking section ends at a vivarium holding live olms — blind cave salamanders nicknamed “baby dragons” that can survive years without food and exist nowhere outside this karst.

When to Go

This is a Claude judgement call, not a measured fact: the cave is busiest through July and August, when the 10:00 and 12:00 departures can sell out two to three days ahead. Early-morning or 14:00/16:00 slots run noticeably quieter, and the shoulder months of May, June, September and October keep the crowds down while the weather outside is still pleasant. Winter departures are fewer — two or three a day — but the temperature inside never changes, which makes it one of the better indoor options on a cold or wet day.

Planning Your Visit

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Look closer

Three Things to Look For

Getting There and What Else Is Nearby

Postojna is 55 km from Ljubljana, about 45 minutes to an hour by car via the A1 motorway; the cave is a short signposted drive from the Postojna exit, and buses and trains from Ljubljana also stop in Postojna town, about 1.5 km from the entrance.

If you’re coming from the coast, Postojna sits almost exactly halfway between Ljubljana and Trieste, roughly 40 minutes from either direction. Predjama Castle is barely 9 km away — manageable as a second stop the same day. Further into the karst, Skocjan Caves and the smaller Vilenica and Krizna caves round out the region, all covered in our overview of Slovenian caves and karst.

Postojna or Skocjan?

Postojna is the spectacle; Skocjan is the one people remember most vividly. If you only have time for one, Postojna is the easier, more reliable choice, especially with children or limited mobility. If you can manage the steps, Skocjan is the one worth the detour.

Frequently Asked Questions