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.
Gunung Mulu National Park
The national park has three notable caves: Sarawak Chamber, one of the world's largest underground chambers, Deer Cave, the largest cave passage in the world, and Clearwater Cave, the longest cave system in Southeast Asia. The Sarawak Chamber is long, wide and at least high, yielding a volume of and an unsupported roof span of . Meanwhile, the Deer Cave is at to in diameter. As of October 2018, Clearwater Cave has of explored passages.