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.
Actun Box Ch'iich'
At -183m, Actun Box Ch'iich' (Cave of the Black Birds) is the deepest cave in the country of Belize. Located above Roaring Creek in the Cayo District, it is one of several caves explored and documented by British and Canadian cavers during a three-week expedition in 1989. The cave contains a small stream and has both an upper and lower entrance, making a through-trip possible.