Velebit
There are hundreds of "holes" on Velebit. It has the largest and deepest caves in Croatia. The three-part "Lukina jama" cave is 1392 m deep, making it one of the deepest caves in the world, and the deepest in southeast Europe, while the "Slovačka jama" is 1320 m. What makes it unique is that it is completely vertical, steepest in the world. At the bottom of the pothole is a water course or siphon with branches that are still unexplored. A kind of leech was discovered in the pothole, which has been ascertained to represent a new species, genus and family; it has been named "Erpobdella mestrovi".
Baumann's Cave
The cave is frequently mentioned in the early scientific and travel literature as it has been open to the public with guided tours since 1649 when Valentin Wagner was installed as first cave guide. Baumann's Cave is probably the oldest regularly frequented and guided show cave, at least in Germany. Amongst its most famous visitors was Johann Wolfgang von Goethe. The cave's biggest chamber, the "Goethesaal", is named after him and is fitted with seats and a stage for concerts and plays.