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.
Deer Cave
Deer Cave was known as the largest cave passage in the world until the discovery of Sơn Đoòng cave in Phong Nha-Kẻ Bàng National Park in Vietnam. It is part of the Gunung Mulu National Park, a UNESCO World Heritage Site characterised by amazing caves and karst formations in a mountainous equatorial rainforest setting. 
The Clearwater cave, with approximately of known passages, is considered the longest cave system in Southeast Asia. It is recognised for its clear underground stream, popular with tourists. The Wind cave is located on the same trail leading to Clearwater cave, and is known for its blowing wind. It contains a chamber dubbed King’s Room, a cavern containing huge columns of stone on both the ceiling and the floor. The Lang cave is the smallest of the caves open to the public. However, its size allows up-close opportunities to see some of the common cave inhabitants such as bats and swiftlets.