The Velebit mountain of Croatia has several deep caves with some of the world's largest subterranean vertical drops.
"Lukina jama" cave is 1392 m deep (1996), the deepest cave in Croatia and the deepest in southeast Europe.[1] At its foot, there are ponds and streams including one of the largest known colonies of subterranean leeches (Croatobranchus mestrovi), which has been ascertained to represent a new species, genus and also family.[1] 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.
Other notable caves include the "Slovacka jama" (Slovak pit), (1,320 m deep), "Velebita" (1026 m deep with underground free fall vertical drop of 513 metres ) and "Meduza" (679 m deep).
The cave "Patkov Gušt" is 553 meters deep and the second deepest pitch in the world as of 2007[update].