Lake Cerknica

Lake Cerknica is one of the oddest bodies of water in Europe because for much of the year it is not there. The basin sits on karst limestone riddled with sinkholes and underground channels, so when the autumn rains come the water rises through the ground and fills a lake that can cover several dozen square kilometres, making it briefly the largest in Slovenia, and then by early summer the same holes drain it away and the bed becomes hay meadow crossed by walking paths and cattle. The cycle has puzzled and delighted people for centuries and was described in detail in the seventeenth century by the polymath Valvasor, which made it famous across Europe. When full it is superb for birds and for rowing; when empty you walk across the bottom. A small museum at Dolenje Jezero explains the hydrology with a working model.

What you actually see

• The full lake - the flooded basin in winter and spring, with birds and boats.
• The dry bed - meadows and walking paths across the bottom in summer.
• The sinkholes - the swallow holes through which the water comes and goes.
• The Jezerski hram museum - the working model explaining the cycle.

When to go

The lake is usually full from around late autumn through spring and gone by midsummer, though the timing varies year to year with rainfall, so check locally before going if you want water. Birdwatching is best in spring. Winter sometimes freezes it enough for skating.

Honest expectations

Whether there is a lake at all depends on recent rain, and people arrive to find either a wide sheet of water or a field of hay with no warning; the local museum and tourist office publish the current state. Facilities around it are minimal. When full, access to the shore is limited in places by marsh.

Nearby

Postojna and Predjama are half an hour west; Ljubljana is under an hour northeast.