Postojna Cave & Predjama Castle: Private Day Trip

You have one day — and you want to spend it somewhere genuinely unforgettable.

Postojna Cave is the most visited cave in Europe for a reason. Over 24 million people have passed through its entrance since it first opened to visitors in 1819 — and the experience still stops people in their tracks. An underground railway carries you deep into the mountain, where vast chambers open up around you, filled with stalactites, stalagmites and formations that took hundreds of thousands of years to grow. Inside, you'll also encounter the olm — a blind, cave-dwelling amphibian found almost nowhere else on earth, known locally as the human fish and once believed to be the offspring of dragons.

Nine kilometres away, Predjama Castle completes the picture. Built into the mouth of a cave halfway up a cliff face, it is officially the largest cave castle in the world according to the Guinness World Records — and one of the most visually striking medieval structures anywhere in Europe. Your guide will bring its history to life before you enter: the story of Erasmus of Predjama, the outlaw knight who held the castle under siege for over a year, supplied through a secret tunnel in the rock above.

Throughout the day, your private guide travels with you, sets the context for everything you see, and handles all the logistics — so your only job is to be present.

Visiting Slovenia for more than a day? Postojna Cave and Predjama Castle are included in our Classic Slovenia journey — a private 7-day route through the country's most iconic destinations.

• Private vehicle & guide throughout — no shared groups
• Pickup anywhere in Slovenia — hotel, apartment or resort
• Everything arranged — just show up and enjoy

• The cave railway is the oldest of its kind in the world.

Visitors have been riding into Postojna Cave by rail since the 19th century. The electric train arrived in 1924 — but the original carriages were pushed by hand long before that.

• The temperature inside never changes.

A constant 10°C year-round, regardless of the season outside. A light jacket is essential even in August.

• Some of the formations took longer to grow than modern humans have existed.

The slowest-growing stalactites add just one millimetre every hundred years. What looks small may be older than the Roman Empire.

• The olm can survive without food for up to ten years.

This blind, cave-dwelling amphibian — found almost nowhere else on earth — slows its metabolism so dramatically it can go years without eating while remaining fully alive.

• Predjama Castle held out under siege for over a year — thanks to a secret tunnel.

While enemy forces waited outside, the castle's occupants received food and supplies through a hidden passage in the rock above. The besieging army never worked out how.

• It is officially the largest cave castle in the world.

Guinness World Records recognised Predjama Castle for its scale and its extraordinary integration into the cliff face.

• The castle's most famous resident was killed in the most undignified way possible.

Knight Erasmus of Predjama was struck by a cannonball while using the castle's toilet. It is a documented historical fact.

Prices are shown per person and are based on the day trip described on this page and the number of travelers in your private party. Each traveller is counted as a full participant regardless of age. No child discounts apply to the day trip price.