Planinska jama
Karst cave with an underground river confluence and the largest cave entrance in Slovenia
Planina Cave (Planinska jama) is a 6.6 km karst cave located 10 km north of Postojna. Inside, a rare natural phenomenon takes place – the underground confluence of two rivers, the Rak and the Pivka. This is the largest underground water confluence in Europe.
The cave sits at the base of the Planinsko polje plateau, 60 km from Ljubljana. By car, it's 50 minutes from the capital or 15 minutes from Postojna. It pairs well with a visit to Postojna Cave.
Visits are guided only, with limited group sizes. Unlike the commercial Postojna Cave, there is no underground railway or mass tourism here – this is a place for those who prefer nature in a more natural setting.
The cave entrance is a portal 40 metres wide and 8 metres high – one of the largest cave entrances in Slovenia. The Unica River flows out of the portal, formed inside the cave by the merging of the Rak and Pivka rivers. In summer, water levels are low and the entrance looks like a massive rock arch; in spring after rainfall, the river fills the portal almost completely.
The tourist route follows a lit path of about 900 metres along the underground riverbed. Ceilings reach 30 metres, and walls are covered in ochre and white flowstone formations. The main highlight is the confluence point, where two rivers of different temperatures and colours meet in a single chamber. The temperature inside is +8–10 °C / 46–50 °F.
The cave is home to a population of olms (Proteus anguinus) – the same blind salamanders found in Postojna Cave, but here they live in their natural habitat rather than in a vivarium. Several bat species also inhabit the cave, including the greater horseshoe bat.
Length – 6.6 km of passages, about 900 m accessible to tourists
Entrance portal – 40 m wide, 8 m high, one of the largest in Slovenia
River confluence – underground meeting of the Rak and Pivka, the largest underground water confluence in Europe
Olms – in their natural habitat, no vivarium
Temperature – +8–10 °C / 46–50 °F year-round
The cave has been known since the 17th century – the first documented mention dates to 1689 when Slovenian polymath Janez Vajkard Valvasor described it in his work "The Glory of the Duchy of Carniola." Systematic exploration began in the 19th century, in parallel with research at nearby Postojna Cave. Speleologists gradually mapped the underground rivers and established connections between surface and underground waterways in the region.
In the 20th century, the cave became an important site for karst hydrology research. A tourist trail along the underground river was developed in the 1970s. In 2004, the cave received natural monument status in Slovenia. Today, Planina Cave remains a key site for studying karst processes and underground fauna, while tourist traffic stays minimal.
Admission:
Adults: ~€12
Children (6–15): ~€8
Children under 5: free
Group discounts (10+): inquire on-site
Guided tours only, on a fixed schedule. Tours run in the warm season (April–October); in winter, by prior arrangement only. Check the current schedule and prices on the website or by phone before visiting.
Guided tours only – independent entry is prohibited. Non-slip footwear is essential – the path is wet and slippery in places. Warm clothing required (+8–10 °C / 46–50 °F inside). A flashlight is useful but the main route is lit. Touching formations is prohibited. The cave may be closed during high water levels (usually in spring) – check before visiting.
On-site:
Infrastructure is minimal. Basic restrooms at the entrance. No cafés or restaurants – nearest options in Planina village (1 km) or Postojna (10 km).
Parking: Free gravel lot for 20–30 cars at the entrance.
Wi-Fi: None. 4G mobile signal works at the entrance; no signal inside.
Accessibility: The route is not wheelchair-accessible – the path is uneven, wet, and rocky in places. Moderate fitness required.
From Postojna (10 km, 15 min):
– By car via regional road through Planina. Follow signs to Planinska jama
– Taxi from Postojna – approximately €15
From Ljubljana (60 km, 50 min):
– By car via A1/E61 to Postojna exit, then through Planina
– Public transport is inconvenient: train to Postojna + taxi. Car rental is the best option
On-site:
From the car park to the cave entrance – 5–10 minute walk along a forest trail.
Season: April–October is the main tourist season. In winter, tours are available by prior arrangement only.
Time of day: Morning tours have fewer visitors. Check the schedule – groups depart at fixed times.
Duration: 1–1.5 hours for the tour. Easy to combine with Postojna Cave or Predjama Castle – all three sites are within a 15 km radius.
Avoid: Heavy rainfall periods (usually spring) – the cave may close due to rising water levels. Check status before your trip.
Practical answers about visiting, routes and time on site.
Adult ticket is approximately €12, children 6–15 about €8, under 5 free. Guided tours only. Verify current prices before your visit.
Planina is natural, with no underground train and minimal tourism. Its main draw is the underground river confluence and olms in the wild. Postojna Cave is commercial, with a railway and vivarium. The two are 10 km apart – easy to visit both.
In winter, tours are by prior arrangement only – they don't run on a regular schedule. The main season is April–October. Contact the cave in advance.
Essential: non-slip shoes (the path is wet) and a warm jacket (+8–10 °C / 46–50 °F inside). A flashlight is helpful. No helmets or ropes needed – the route is developed.
Public transport is impractical. The nearest station is Postojna (10 km), then a taxi for ~€15. Best option: rent a car and combine with Postojna Cave and Predjama Castle.
For children aged 6–7 and up who can walk 900 m on a wet path – yes. Not suitable for small children or strollers. Requires minimal fitness.
Yes, olms live in the underground river. The guide will point out spots where they can be seen. Unlike the vivarium at Postojna Cave, these are wild olms – sightings aren't guaranteed.
During heavy, sustained rainfall, underground river levels rise and the cave may close. This most often happens in spring. Check status by phone on the day of your visit.
