Less famous than the renowned Postojna caves, the caves at Skocjan in southwestern Slovenia near the coast are certainly no less impressive and more important from a scientific point of view. They are the classic karst caves and are much less polluted than others, forming their own ecosystem and hosting several endemic species. Besides, they are extremely impressive, with huge stalactites and stalagmites, a river running through it and a mighty canyon with a footbridge 40 metres above the water that makes your knees shudder... The guided tour takes about an hour and a half and is pretty strenuous, since from about the halfway point it is mostly uphill over slippery steps. Despite this, a visit there is just fascinating and highly recommended.