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.
Phong Nha-Kẻ Bàng National Park
Sơn Đoòng Cave (in Vietnamese: Hang Sơn Đoòng, meaning Mountain River Cave) is a relatively recently discovered cave in the national park. Found by a local man and explored and publicly announced by the British cave scientists of the British Cave Research Association, it is regarded as the largest cave in the world. The biggest chamber of Sơn Đoòng is over five kilometers in length, 200 meters high and 150 meters wide. With these tremendous dimensions, Sơn Đoòng overtakes Deer Cave of Malaysia to take the title of world's largest cave. Because the fast flowing underground river in the cave deterred the explorers from going farther, they were only able to estimate the length of the cave using a flashlight.