Planina Cave is one of the longest active caves in Slovenia and the subterranean bed of the Unica River. It's a place where two underground rivers meet beneath the earth, creating one of the largest confluences of subterranean rivers anywhere in Europe.

The entrance opens in the southwestern part of Planina Polje, tucked into a gable-end valley beneath rocks rising 65 meters high. Five hundred meters inside, the Pivka River — flowing from the Postojna Polje through Postojna Cave — meets the Rak River, which arrives via Weaver Cave from Rak Škocjan. The cave stretches an impressive 6,656 meters and reaches a subterranean depth of 65 meters. Inside, the air is cool and damp year-round, and the constant rush of underground water fills the huge tunnel-like passages. Above ground, Planina Polje offers a scenic, quiet landscape that changes dramatically with the seasons, especially when water levels rise after heavy rain or snowmelt.

How to get there

• From the village of Planina or the area near the former Little Castle — approach on foot to the main entrance, moderate difficulty depending on route conditions
• Access is also possible from Planina Polje, where the rocky cliffs above the entrance are clearly visible

Practical information

• Exploring the interior is only possible on organized caving tours due to the active underground river system
• Water levels vary seasonally, affecting access to certain parts of the cave

Water tracing has confirmed a connection between the Planina Cave and Postojna Cave systems — once fully explored by cavers, the joint system could exceed 31 kilometers in length.