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.
Lechuguilla Cave
The cave was visited infrequently after mining activities ceased. However, in the 1950s, cavers heard wind roaring up from the rubble-choked cave floor. Although no route was obvious, people concluded that cave passages lay below the rubble. Led by Dave Allured, a group of cavers from the Colorado Grotto gained permission from the National Park Service and began digging in 1984. Since the breakthrough into large walking passages occurred on May 26, 1986, explorers have mapped over of passages, making Lechuguilla the eighth-longest cave in the world and fourth-longest in the United States. Lechuguilla was also the deepest known cave in the continental United States until the exploration of Tears of the Turtle Cave in 2014. Drawn by the cave's pristine condition and rare beauty, cavers come from around the world to explore and map its passages and geology.