Velebit caves
The "Lukina jama" cave is 1431 m deep (2013), the deepest cave in Croatia, 14th deepest cave in the world and the deepest cave in southeast Europe. At its foot, there are ponds and streams including one of the largest known colonies of subterranean leeches ("Erpobdella mestrovi"), which has been ascertained to represent a new species, genus and also family. Other species discovered in the system, include the air-breathing land snails "Zospeum tholussum". Like Lukina jama, Slovacka jama, Velebita and Meduza are also located at the "Hajdučki i Rožanski kukovi" special reserve, a dedicated part of the Sjeverni Velebit national park.
Chevé Cave
Chevé Cave was discovered in the mid-1980s by Bill Farr and Carol Vesely. Since then it has been pushed to the depth of , making it the second deepest cave in the Americas. The cave system has the greatest proven depth potential in the world as proven by a dye trace from its main entrance to the resurgence 2547 meters lower. The current terminus of the main Chevé system is a large breakdown pile reached after diving through two sumps. It is just over 9 kilometers from the entrance, making it currently one of the most remote underground locations on earth. Due to the logistical difficulties of continuing exploration from this point, current expeditions are focusing on finding mid-way entrances that might provide a quicker route into the middle Chevé system.