Postojna

Postojna needs a day, almost entirely dedicated to Postojna Cave, a system of over 24km partly explored by underground train. May-September is peak season, though the temperature inside the cave stays constant year-round. It's inexpensive compared to other European natural attractions of similar scale. Its caves are home to the «baby dragon» (Proteus anguinus), a blind amphibian that can live over 100 years without eating, and it's one of the most visited karst cave systems in the world.