Which river disappears underground into Slovenia's Škocjan Caves?

The Reka River disappears underground into Slovenia’s Škocjan Caves.

The Reka flows across the Karst Plateau before sinking beneath a rocky wall at the Big Collapse Doline. It then travels through the cave system and the wider karst underground, eventually re-emerging in Italy near Monfalcone at the springs of the Timavo River. The underground course is about 34 kilometres long.

This disappearing river helped create Škocjan’s immense canyon, passages and chambers by dissolving and enlarging limestone over long periods. One of the major passages is Hanke’s Channel, which is roughly 3.5 kilometres long and in places more than 140 metres high. Martel’s Chamber is among the largest known underground chambers in Europe.

The Reka is easy to confuse with Slovenia’s better-known surface rivers, including the Soča, Drava and Sava. Those rivers do not provide the defining underground watercourse of Škocjan. The caves became a UNESCO World Heritage Site in 1986 and are also internationally important as a karst wetland.