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.
Other notable caves include the "Slovacka jama" (Slovak pit), (1,320 m deep), "Velebita" (1026 m deep with underground free fall vertical drop of 513 metres ) and "Meduza" (679 m deep).
- Radovan Radovinovič, The Croatian Adriatic Tourist Guide, pg. 143, Zagreb (1999), ISBN 953-178-097-8
- Alexander M. Weigand (2013). "New Zospeum species (Gastropoda, Ellobioidea, Carychiidae) from 980 m depth in the Lukina jama–Trojama cave system (Velebit Mts., Croatia)" (PDF). Subterranean Biology. 11: 45–53. doi:10.3897/subtbiol.11.5966.
- D.Bakšić, A.Bakšić (2008). "Speleological exploration of pit Patkov gušt". Croatian speleological server. Retrieved 9 June 2012.