6. Postojna Cave and Predjama Castle
One of Slovenia's most fascinating natural wonders lies hidden inside its karst rocks. Postojna cave, with its beautiful halls and cave formations, is a maze of beauty. You are in for an exciting ride through the cave with an electric train, and some exploration on foot. Next, visit the majestic Predjama castle, perched for over 800 years in the middle of a 123-meter-high cliff. Spend a memorable day exploring the cave and touring the mysterious castle, then meet baby dragons at the nearby Vivarium, an onsite research center and museum.