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".
Lurgrotte
The Lurgrotte karst cave is the largest cave in the Eastern Alps of Styria, Austria. It is located about north of Graz and crosses the Tannenben karst region. The cave has two accessible entrances, one at the village of Semriach and the other at the village of Peggau. At the Semriach entrance, the Lur River sinks into the cave. At the Peggau entrance, the Schmelz River emerges from within the cave, flowing to the west and eventually joining the Mur River.