Though the impressive red-roofed castles in Loka and Ljubljana dominate their respective skylines, our favourite Slovenian castle is surely Predjama, a massive 12th-century fortress hewn out of solid rock. The largest 'cave castle' in the world, Predjama is cut into the side of a 400-foot (123m) cliff, and backs onto a massive network of secret passages that tunnel deep into the rock. Dripping with medieval romance, visitors can hear heroic legends of grand sieges and rebellious knights, or scout out the vast bat colony in the castle caves.