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.
István Cave
The cave is still being explored, but only a part can be visited. Its deepest known area is named "Hell". The most beautiful dripstone structures are the "Mammut's Mouth", "Fairyland", "Column Hall" and "Concert Hall". Due to water filling the cave in 1958 and 1974, the inner caverns are presumably connected with water drains.