Cave "Prohodna" (passable) aka "Eye Cave" is located near Karlukovo about 80 km to the north of Sofia. As evident from its name, it is passable, that can be accessed from one side and out the other. The cave is very beautiful and easily accessible, can be visited with children. The height of the arch is about 50 meters and above can be bungee jumping. Many famous Bulgarian movies were filmed in this cave.