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.
Titan (cave)
Titan is a natural cavern near Castleton in the Derbyshire Peak District, and is the deepest shaft of any known cave in Britain, at . The existence of Titan was revealed in November 2006, following its discovery on 1 January 1999 after cavers discovered connections from the James Hall Over Engine Mine to both Speedwell Cavern and Peak Cavern. Previously, the deepest known underground shaft in Britain had been Gaping Gill on the slopes of Ingleborough in the Yorkshire Dales.