Postojna Cave is Slovenia's great underground wonder and one of the most famous caves in the world. Over more than two million years, the Pivka River wore away the Karst limestone until it had carved a labyrinth of more than 24 kilometres of passages, gigantic halls and forests of stalactites and stalagmites. The amazing part is how you visit it: a little open electric train heads several kilometres underground through lit tunnels, before the tour continues on foot through the most spectacular halls. It's a unique experience that has been running since 1872.
Inside awaits a world of incredible formations with names of their own: the Brilliant (Briljant), a gleaming white 5-metre stalagmite that has become the symbol of the cave; the Spaghetti, ultra-thin stalactites hanging from the ceiling; the Concert Hall, so big that recitals are held there with perfect acoustics. And a living star: the olm (Proteus anguinus), the 'baby dragon' or human fish, a blind amphibian that lives up to a hundred years in the dark and can be seen in the Vivarium.
This guide helps you plan your visit: how much the ticket costs (it isn't cheap) and how to save with the combined ticket with Predjama Castle, how long the tour lasts, the best time to avoid queues, how to get there from Ljubljana or the coast, and why booking ahead pays off. Postojna is the great classic of the Slovenian Karst, a must on any trip to the country, and it pairs wonderfully with the cave castle of Predjama a few kilometres away.
The Postojna Karst has been inhabited and explored since ancient times: there is graffiti in the cave dating from 1213, and the first halls have been known for centuries. But the modern history of the cave begins in 1818, when local man Luka Čeč, preparing the cave for a visit by Emperor Ferdinand I of Austria, ventured beyond the known passages and discovered the inner galleries, revealing the true scale of the system. In 1819 it officially opened to tourists, and Postojna soon became one of Europe's great attractions. In 1872 the first tracks of the underground railway were laid, first pushed by hand and later pulled by a locomotive, which made the visit world-famous. In 1884 the cave got electric lighting, before many cities did. During the First and Second World Wars the cave was used for military purposes; in 1944 the partisans blew up a German fuel depot set up inside, damaging some of the formations (you can still see the blackened rock). Since then, millions of visitors — more than 40 million in total — have toured it. The full story is on our history page.
Read the full history ↓Mediterranean Slovenia: the limestone plateau of the Kras, which gave the world's “karst” its scientific name, its colossal caves, the imperial stud farm of the Lipizzaner horses and a short stretch of Istrian coast with a Venetian feel, between Koper, Piran and Portorož.
Read the history of The Karst and the Adriatic coast →Some places make no sense on your own; with someone explaining them, they change completely. We look ours up on Civitatis: guided in Spanish and booked online with no fuss. They have 8 activities in Liubliana. And there are free tours here: you book without paying and tip the guide whatever you think at the end, so trying one costs you nothing. Have a look below: tap any of them to see them all.
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Origins, formation and what the sources say.
The story of Postojna Cave begins long before any human story, on a timescale that is hard to imagine. More than two million years ago, in the Slovenian Karst region (the Kras, which gave its name to every 'karst' landscape in the world), the Pivka River began doing what water does to limestone: dissolving it, drop by drop, crack by crack. Limestone is a porous, soluble rock, and wherever water finds a fissure, it widens it. Over geological time, those fissures become channels, the channels become passages and the passages become enormous chambers.
That is how a system of more than 24 kilometres of passages on several levels was carved out in total darkness, one of the longest in Europe. The Pivka, which disappears underground on the surface of the Karst, still flows today through the lower levels of the cave, unseen but active, carrying on its work. And where water drips from the ceiling, each drop leaves behind a tiny amount of calcite. That is how stalactites form and hang from the roof, how stalagmites rise from the floor and, when the two meet, how columns are born. All of it happens incredibly slowly, at barely a millimetre a year or less.
That patient work produced the wonders that now have names of their own: the Brilliant, the dazzling white calcite stalagmite that has become the symbol of Postojna; the Spaghetti, very fine tubes hanging from the ceiling; and curtains, flowstones and stone 'organs'. When the first visitors walked in with torches, they found a landscape that had been taking shape for two million years in absolute darkness, waiting to be seen.
Postojna's worldwide fame is modern, but the people of the Karst had known the cave mouth and its first chambers since ancient times. The most telling proof is written on the rock itself: one of the passages holds graffiti dated 1213, one of the oldest records of people in the cave, alongside signatures and dates left by other visitors over the following centuries. Locals went into the accessible parts to take shelter, to explore or simply out of curiosity.
For centuries, however, only the first part of the system was known, the part closest to the entrance. The rest, the kilometres of inner passages that amaze visitors today, stayed hidden behind difficult passages and underground water. The cave appeared in some accounts and maps of Carniola, the historical region it belongs to, and it was a local curiosity, but nothing compared with what was to come.
The Karst as a whole already fascinated naturalists. The scientific name for this type of landscape, 'karst', comes from this Slovenian region, and features such as rivers that vanish underground, sinkholes and caves were the subject of both study and legend. Postojna, with its river plunging into the mountain, was a key part of that mysterious landscape. All it needed was someone brave enough to go beyond the known.
The year that changed Postojna's history was 1818. Emperor Francis I of Austria was about to visit the cave, and a group of local workers was preparing and lighting the known passages to receive him properly. Among them was Luka Čeč, a lamplighter and caretaker of the cave. During the work, Čeč dared to cross a point that until then had marked the end of the explored area and, pushing further in, discovered the vast inner galleries that nobody had ever seen: the great chambers, the forests of stalactites, the real heart of Postojna.
The find revealed in one stroke that the cave was far bigger and more spectacular than anyone had thought. The following year, in 1819, the cave officially opened to visitors, and Postojna quickly became one of the great attractions of the Austrian Empire and of all Europe. An administration was set up, guides were appointed, a register of distinguished visitors was kept (emperors, kings, scientists, writers) and the cave began to appear in 19th-century travel guides as a must-see.
Luka Čeč, the man who had opened the door to that world, became linked to Postojna forever, although, like so many humble discoverers, he did not receive the recognition he deserved during his lifetime. His daring, on the other hand, set off a tourism industry that is still going strong two centuries later and has brought more than forty million people to explore the depths of the Karst.
The 19th and early 20th centuries were Postojna's golden age, marked by innovations that made it unique. The most famous came in 1872, when the first tracks of an underground railway were laid inside the cave. At first the carriages were pushed by hand or rolled by gravity, then came a small steam locomotive (with all the smoke problems you can imagine in an enclosed space) and finally, in 1914, the train was electrified. That little open train heading deep into the mountain became Postojna's trademark and an attraction in its own right, something almost no other cave in the world has copied.
Modernisation continued with light. In 1884, Postojna installed electric lighting inside the cave, ahead of many European cities that were still lit by gas. Being able to walk through the passages under electric light, with no torches and no smoke, transformed the experience and finally let people appreciate the beauty of the formations. At one point the cave even had a post office inside with its own postmark, music in the Concert Hall (whose size and acoustics amazed everyone) and all the trappings of a first-class tourist destination.
Political geography also played its part in those glory days. Postojna belonged to Austrian Carniola and lay very close to the border with the Italian world. After the First World War, the area passed to Italy, which also ran the cave as a tourist attraction. Kings, aristocrats, scientists and travellers from all over Europe filed through its passages, and Postojna cemented its reputation as one of the continent's underground wonders, a place you had to see at least once in your life.
The 20th century also brought Postojna its darker hours. During the Second World War, when the region was under occupation, German forces used part of the cave as a military depot and stored large quantities of aviation fuel inside, taking advantage of the natural shelter the mountain offered. The cave, made to amaze, became war infrastructure for a while.
In 1944, the Slovenian Partisan resistance attacked the depot. A sabotage operation set the stored fuel alight, causing a fire that burned for days inside the cave. The flames and smoke damaged some of the formations and blackened the rock in several passages near the entrance. Even today, guides point out those stretches of soot-darkened stone, a visible scar that shows not even a two-million-year-old natural sanctuary was spared from the conflict.
After the war, Postojna became part of socialist Yugoslavia, within the Republic of Slovenia. The cave was restored as a tourist attraction, and its management and lighting were gradually modernised. Throughout the second half of the 20th century, millions of visitors from across the Eastern Bloc and abroad kept coming, and Postojna remained one of the great tourism icons, first of Yugoslavia and, from 1991, of independent Slovenia.
21st-century Postojna combines mass tourism with science and conservation. Hundreds of thousands of people visit every year, and the all-time total is comfortably over forty million, making it the most visited show cave in Europe. The company that runs it has expanded what it offers with the Expo of the Karst, the Vivarium and joint management of Predjama Castle, a few kilometres away, creating a large Karst park.
The scientific star is the olm (Proteus anguinus), the 'baby dragon' or 'human fish', a blind amphibian found only in the caves of the Karst, which can live for a century and survive for years without food. Postojna has a laboratory dedicated to studying it, and in 2016 the whole world watched in amazement as, for the first time in a tourist setting and on camera, several olm eggs hatched inside the cave. That event was a reminder that Postojna is not just a show but a living, fragile underground ecosystem, with some of the richest cave biodiversity on the planet.
Today, a visit to Postojna is a journey through deep time: two million years of patient water, eight centuries of graffiti and visitors, two centuries of modern tourism and the scars of the 20th-century wars, all in an hour and a half underground. From the 1213 graffiti to the olms in the lab, from Luka Čeč's discovery to the electric train, the cave in the Slovenian Karst keeps doing what it has done from the very beginning: leaving anyone who dares to go down and see it speechless.
