Postojna Cave

Postojna Cave: You Board a Train Inside the Mountain

The tour of Postojna Cave begins with a three-minute ride on a narrow-gauge electric railway that carries visitors 2 kilometres into the limestone mountain. This is not a detail or an analogy. You board a small train at the cave entrance, and it moves at a moderate speed through passages of stalactites and stalagmites in the dark before depositing you in the deeper sections. The railway has been operating since 1872, making it one of the world’s oldest tourist railways. The cave itself has been attracting visitors since the Habsburg court came in the 1820s. The tourism infrastructure here is old, well-organised, and has clearly thought about what it is doing.

Postojna is the most-visited attraction in Slovenia and the most extensive cave system open to the public in Europe, with 24 kilometres of explored passages and a visitor route of about 5.7 kilometres. The cave formed over 3 million years as the Pivka River dissolved limestone, entering the system underground and exiting 3 kilometres later.

The Tour

The standard tour takes about 1.5 hours and covers the sections called Brilliant and Concert Hall, the latter a chamber large enough to seat 10,000 people and occasionally used for actual concerts by touring orchestras and ensembles. The cave temperature stays at 10 degrees Celsius year-round, regardless of what is happening above. Bring a jacket or fleece even in August.

Photography is permitted but challenging given the low light. Tripods are not allowed on the tour route. Advance booking is strongly recommended from April through October; tours fill in peak season and walk-up queue times can extend to two or three hours. Book online at postojnska-jama.eu.

The Olm

The cave’s most unusual resident is the olm (Proteus anguinus), a blind aquatic salamander that lives its entire life in underground water systems. It grows to about 25 to 30 centimetres, has translucent pinkish-white skin, vestigial eyes covered in skin, external gill-like organs, and a documented lifespan of up to 100 years. It can survive more than a decade without food. When Slovenian peasants first documented it in the 17th century, they reportedly believed the young ones were baby dragons, which looking at the creature is an understandable response.

The olm appears on Slovenian euro coins of lower denomination. The cave maintains a vivarium (Proteus Exhibition, separately ticketed) where olms are visible under conditions approximating their natural habitat.

Predjama Castle

Nine kilometres northwest, Predjama Castle is a Renaissance fortress built into the mouth of a cave high in a cliff face. The current building dates from the 16th century. Its cliff-face position meant it could only be approached from below, making conventional siege nearly impossible. According to local history, the knight Erasmus of Lueg held out inside for a year before being killed by a cannonball in 1484 – the siege succeeded in the end, but the structural position made it take far longer than it should have. A combined ticket covers both the cave and the castle.

Practical Notes

Postojna is 53 kilometres southwest of Ljubljana, about 45 minutes by car or 1.5 hours by train (the station is 2 kilometres from the cave entrance). The cave entrance costs around 28 to 32 euros for adults depending on season. Avoid Sundays and public holidays in July and August for the lightest crowds. A weekday morning in May, June, or September gives the same caves with far fewer people.