Prohodna Cave is one of the most famous and easily accessible caves in Bulgaria. It lies 2 km away from Karlukovo Village and 112 km away from Sofia. The cave is a natural 262 m long rock bridge. It has two entrances – a big and a small one. A path beginning at the approximately 35 m-high small entrance crosses the cave and goes out through the big entrance - the biggest cave arch in Bulgaria – 45 m.