The cave under The Predjama Castle
Under the Predjama Castle, the underground stream Lokva formed an underground cave, whose tunnels are divided into four levels. The highest level is represented by Erazem's Hole and Fiženica. An entrance into the Horse Barn and Name Tunnel (Main or Old Cave) leads into the second level where researches discovered signatures of visitors from the 15th century onwards. The third level is more pronounced in the entrance part. The fourth, and the youngest, is an active sinkhole cave of the Lokva stream, closed by a siphon, behind which lie undiscovered waterways, which lead to Vipava.
A part of the cave, the so called Western Tunnel, can be visited only by experienced cavers and enthusiasts, for the passage through narrow parts can be quite difficult. With appropriate caving equipment, an especially adventurous tour with a guide can be organised by booking in advance, of course.