Kostanjevica Cave, opened up by a flood

A cave that opened itself

It lies at the foot of the Gorjanci hills, in karst terrain of Cretaceous limestone. The Kostanjevica na Krki caving club, which runs it, explains that rainwater, underground streams and tectonic shifts shaped its formations over thousands of years. In 1937 a flood broke through today’s entrance, and the cave quite literally opened itself to the people living nearby.

In 1971 electric lighting was finally installed, along with 300 m of path through the most striking sections. Today just over two kilometres have been explored, and the research into the wider cave system goes on.

What’s inside

The tour, 45 to 60 minutes and always guided, takes in the hall of stalactites and stalagmites, an underground lake of very clear water and the Cross Hall. The temperature holds at 10 to 12 °C all year, so you’ll want a jacket even in August, plus closed shoes because the floor is damp and uneven. Groups are capped at 30, and tours are given in Slovenian and English, with German, Italian and Dutch available for groups that book a few days ahead. There are toilets by the entrance but no café, so bring water and a snack, and the club accepts both cash and cards. Personal photos are allowed, though not with flash near the bats.

Bats and other residents

The cave is a key winter roost for several bat species, all legally protected, which hibernate from October to April. That’s why, in a normal season, it shuts from November to mid-April. The club asks visitors not to use flash near the roosts and doesn’t allow pets. Cave spiders, beetles and amphibians live inside as well.

Once your dates are set, check which hotels are still free in Kostanjevica na Krki before prices climb.

When it reopens: seasons and prices

In the last season it opened from mid-April to the end of June at weekends and on holidays, every day in July and August, and again at weekends in September and October, always 10:00 to 18:00. Tickets cost €12 for adults, €8 for students, €6 for children aged 5 to 14 and €30 for a family, with under-4s free. They may change after the works.

Fitting it into the area

The cave is one or two kilometres from Kostanjevica na Krki, so it pairs well with the monastery gallery. The club puts it about 20 km from Brežice and its castle. If you’re after the big show caves, my guide to caves in Slovenia covers the rest.

If you would rather have a local show you round, book a guided tour in Kostanjevica Cave and choose by the reviews.

Once your dates are set, check which hotels are still free in Kostanjevica na Krki before prices climb.