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.
Lazareva Pećina
The Lazareva Pećina, which translates Lazar's Cave, is the longest explored cave in Serbia. Located in Bor municipality, near Zlot, the cave is also sometimes referred to as Zlotska Cave. According to 2012's "Recent Landform Evolution: The Carpatho-Balkan-Dinaric Region", the cave is long. The cave is situated near the entrance of the deep canyon carved into the mountains by the river Zlotska.