One of Slovenia’s four World Heritage Sites is ?kocjan Caves, one of the largest underground canyons in the world and home to four miles of underground passages, vast chambers, and waterfalls. Postojna Cave, meanwhile, is the country’s most visited attraction. Its formations of stalagmites and stalactites are unrivalled anywhere and it is home to the endangered Proteus anguinus, a blind salamander known as “the human fish” because of its pinkish skin colour.