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Photo: Doremo, CC BY-SA 3.0 via Wikimedia Commons
A 6.5km long cave connected (by yet undiscovered path) to Postojna Caves. The huge entrance and around 200m path can be freely visited, but to explore deeper a guided tour must be booked.
Planina Cave, formerly also Little Castle Cave after Little Castle in the vicinity of its entrance, is one of the longest Slovenian active caves. It is a huge tunnel and the subterranean bed of the Unica River. It is located in Inner Carniola. Five hundred meters from the entrance into the cave is a confluence of two underground rivers: the Pivka River, flowing from the Postojna Polje through Postojna Cave, and the Rak River, flowing to Planina Cave through Weaver Cave from Rak Škocjan. This is one of the largest confluences of subterranean rivers in Europe.
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Open every day. The caves were created by the Pivka river over millions of years. The cave system has three levels. The Pivka River flows through the lower level, so the cave is still expanding today.A total of 175 species live in the caves of Postojna. Of these, 115 are troglobionts, which means that they occur exclusively in caves. The most important of these is the olm, which can be seen during the cave tour.As water droplets containing various minerals fall to the ground, they gradually precipitate out the minerals, forming stalagmites, also known as standing stalactites. The stalactites you will see are up to 500,000 years old. The most famous stalagmite in the Postojna Cave is the Brilliant, a 5 metre high, snow-white standing stalagmite in the centre of the cave. Tourists are transported inside the cave by electric train. The train takes about 3.5 km and the guided tour on foot is 1.5 km. From the cave entrance, the train runs through narrow passages, but there are parts of the cave where a cathedral could be built. The cave system includes a concert hall, which has been in use since the 19th century and can host up to 10,000 people. Containing 20 km of underground galleries, chambers and corridors, up to 50 meters high in places. Tours begin with a train journey into the cave system through several chambers before visitors get off and do a guided walk through stalagmite studded caverns. The train then returns you to the surface. The whole tour lasts 90 minutes. Tall travelers beware - the cave ceiling is very low in many parts of the train journey with sharp protrusions from the cave walls, and the train runs quite fast, so keep all bodily limbs (and children) well inside the moving vehicle! Other longer and more strenuous tours ("Underground Adventures") are available to groups of 2-50 people. The caves are damp and chilly (10 C year round) so appropriate shoes and clothing should be worn. €25.80/20.60/15.50 adult/student/child. Start of guided tours is at 10.00, 12.00, 14.00 from October to April and on every hour on the hour between 9.00 and 18.00 from May to September.
Rakov Škocjan
A carst valley around a river (may be partly dry depending on the seasons), which in places disappears into the ground. Various foot paths around the river will take you into magnificient caves, picturesque valleys and under carst stone bridges "Velki naravni most" and "Mali naravni most". The latter one, despite the name, is the larger area, and also a somewhat more interesting.
A remarkable looking castle that looks like it is growing out of a cave. Home to the legendary medieval knight of Erazem Predjamski who was besieged in this castle for several months for tax evasion. It did not end well for Erazem, but the legend was started. Located 9 km away from Postojna. You can tour the castle and the caves below it (caves may require prebooking).