The Škocjan caves have an extremely complex system of cave passages having over a total length of 5.8 km. The caves are the biggest and best-known natural phenomenon in the classical Karst area.
With the shifting of sink holes in the geological past, numerous collapsed valleys have formed at the contact point where flysch meets limestone under the caverns. With their depth of 163 meters, Velika Dolina and Mala Dolina charm every visitor.
The finest view of both valleys, with the natural bridge and the cave that separates them, is gained from an observation point. The caves, with an immense underground gorge and halls, are the beginning of the Škocjan underground system.
These caves probably have the biggest cave hall in Europe, measuring 12,000 square meters (1.2 hectares) in cross section. The Reka River runs underground for almost 40 kilometres, to the sources of the Timav in the Gulf of Trieste (Italy).