Predjamski grad, or Castle in Front of the Cave, is an amazing looking castle near Postojna,
Slovekia Slovenia. Here's the story of the castle, by Flickr user JumpinJack:
Legend says that none of Ravbar's men knew where Erazem's stronghold is. So Erazem himself, cheeky as he was, put on a diguise and offered to lead them to it. Be as it may, as they found out the location, they laid the siege to the castle for months. When they froze their bums off in the middle of winter, Erazem allegedly catapulted a roasted ox from the castle and wished them good appetite.
When spring arrived, Erazem started to send them freshly picked cherries. Ravbar was thoroughly puzzled by this. There were rumours among his men, that there was a sort of paradise land in the caves behind the castle, that yields all sorts of crop throughout the year...
Little did they know, that there's a passage through the cave, which exits on the other side of the hill. Probably this passage and the elaborate cave system were the main reason why the castle was built there in the first place.