Postojna is approximately 53km southwest of Ljubljana. The bus from Ljubljana Bus Station takes approximately one hour (approximately €6 single); the train from Ljubljana Station takes around 1 hour 10 minutes and deposits you at Postojna station, a 15-minute walk from the cave entrance. Buses and trains run regularly; the bus is marginally more convenient for a day trip.
The Ljubljana Marathon finishes on 18 October. Both Postojna Cave and Predjama Castle are fully open in October; they are among Slovenia's most-visited sites and run year-round. October sees visitor numbers reduce from summer peaks without any operational reduction.
October at Postojna: The cave maintains a constant 10°C throughout the year regardless of exterior temperature. After running a marathon in 5--14°C conditions, descending into a 10°C underground environment requires a warm mid-layer. The exterior temperature at Predjama Castle will be autumn cool; a waterproof is advisable.
Postojna Cave (Postojnska Jama)
The cave system at Postojna extends for 24km; the public tour covers approximately 5.7km in 90 minutes. The first 3.7km of the tour is by narrow-gauge electric train that travels at approximately 10km/h through the main passage; the final 2km is on foot through the concert hall, the White Cave, and the cave spaghetti formations. The cave has been illuminated for tourists since 1819; the current lighting installation is LED.
What to expect: The scale is the primary experience. The main Concert Hall (Koncertna dvorana) is 10,000 square metres and has genuine concert-hall acoustics - it hosts events seating over 10,000 people on occasions. The formations include 5-metre stalagmites, 15-metre ceiling stalactites, and formations that grew for over 5 million years. The cave contains the human fish (Proteus anguinus), a blind cave salamander unique to the Dinaric karst system; it can be seen in a vivarium near the exit.
Entry approximately €30 (includes cave train); book online at postojnska-jama.eu during October to confirm availability. The cave entrance is a five-minute walk from the bus stop on Titova cesta.
The Vivarium Proteus is a separate ticket (approximately €15) covering the research display on the Proteus anguinus and other cave species. Optional but well-executed.
Predjama Castle (Predjamski Grad)
Predjama is 9km from Postojna. No direct public transport connects the two; options are taxi from Postojna (approximately €15 each way), a combined shuttle sold with the cave ticket, or a rental car. The cave website sells a combined ticket and shuttle - the most practical solution for a day visitor without a car.
The castle is built into a cave opening in a 123-metre cliff face: a fortification using the cave as its back wall and extending out over the abyss in several stages of construction between the twelfth and sixteenth centuries. It is occupied most famously in the legend of Erasmus of Lueg, a Slovenian robber baron who held the castle against a Habsburg siege for over a year and was eventually killed when a cannonball struck the latrine. The cannonball socket is still visible.
The interior tour covers seven floors accessible by steep internal stairs. The castle kitchen, the dungeon, the secret passage through the cliff, and the rooftop views over the karst valley are the principal attractions. Entry approximately €19; included in the combined Postojna-Predjama ticket (approximately €43, plus shuttle transfer). Allow 90 minutes.
Combined Day Timing
A realistic day from Ljubljana:
- 08:00 departure from Ljubljana Bus Station
- 09:00 arrive Postojna
- 09:30 enter cave (tours start every 30 minutes in season)
- 11:00 exit cave; lunch at one of the restaurants near the cave entrance
- 12:30 shuttle or taxi to Predjama Castle
- 13:00--14:30 Predjama Castle tour
- 15:30 taxi back to Postojna
- 16:00 bus to Ljubljana (approximately hourly)
- 17:00 arrive Ljubljana
Where to eat near Postojna Cave: Gostilna Požar on Titova cesta is the most convenient for a midday break between the cave and the castle. Simple Slovenian food, adequate.
Škocjan Caves (Alternative)
If Postojna Cave does not appeal or is sold out, Škocjan Caves (35km southwest of Postojna) is the other Slovenian cave UNESCO site - smaller in total length but containing one of the largest underground canyons in the world. Access by car is most practical. The two caves are different in character and both worth visiting on separate days; combined on one day is too much.