See Inside the World’s Largest Cave Castle

But the real showstopper isn’t the king’s chambers or the armory, but the connected cave and series of underground tunnels buried deep into the cliffside. Though the structure has roots as far back as the 13th century, the most famous tale featuring the impenetrable edifice begins a couple hundred years later during the 15th century. According to the legend, the castle became the hideaway for Erazem Lueger (also known as Erasmus), the son of Nikolaj Lueger, the imperial governor of Trieste.

After carrying out a vengeful murder, Erazem, who was a known robber baron, enraged the House of Habsburg and quickly found himself in a battle with the Roman Empire. He found safety in the family castle, using the underground tunnels and cave to retrieve food and water without the opposing army noticing. The castle did its job, keeping Erazem safe for months on end. However, the legend states that he was sold out by a servant who lit a torch while Erazem was using the nearby outhouse, leading the Romans to shoot a cannon that killed the knight. 

These days, the cave is now home to a bat colony—not royal kinsmen—but if you’re willing to work around the winged mammals’ hibernation schedule, you can still visit it during the summer, from June through August. The castle, on the other hand, is open to tourists year-round.