Velebit caves

The Velebit mountains of Croatia have several deep caves with some of the world's largest subterranean vertical drops.

[1] 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.

[1] Other species discovered in the system, include the air-breathing land snails Zospeum tholussum.

[2] Like Lukina jama, Slovačka jama, Velebita and Meduza are also located at the "Hajdučki i Rožanski kukovi" special reserve, a dedicated part of the Sjeverni Velebit national park.

The vertical shaft "Patkov Gušt", named after a deceased Croatian speleologist[3] is 553 meters deep and the second deepest pitch in the world as of 2007[update].