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".
Pierre Chevalier (caver)
Chevalier first visited the Trou du Glaz entrance in 1935, and was struck by the possibility of exploring beyond what was at the time considered technically possible. With Fernand Petzl, Charles Petit-Didier and others, Chevalier completed explorations that connected four entrances (Trou du Glaz, Guiers Mort, P40 and Grotte Annette) and established the Dent de Crolles as the deepest cave system in the world (-658m).