Step into Slovenia's magical underworld as you enter Postojna's famous caves. Carved out by the flowing waters of the River Pivka over millions of years, the labyrinthine passages and halls are dimly lit, only just illuminating the fascinating geological features within them. You will explore all 21 kilometers, wandering past dripstone walls, translucent curtains and pillars of varying sizes, each more colorful than the last. As your guide leads you from stalagmite to stalagtite, you'll learn about just how this complex geological structure came to be and the legends which surround it. Once you've surfaced, the day continues with a trip to Predjama Castle. An impressive building which hangs dramatically over you on its 100-meter-high vertical cliff, it was once home to the infamous robber knight, Erasmus. Hear all about his life and about the castle which are both shrouded in mystery before heading back to Ljubljana through verdant green landscapes.