Velebit
There are hundreds of "holes" on Velebit. It has the largest and deepest caves in Croatia. The three-part "Lukina jama" cave is 1392 m deep, making it one of the deepest caves in the world, and the deepest in southeast Europe, while the "Slovačka jama" is 1320 m. What makes it unique is that it is completely vertical, steepest in the world. At the bottom of the pothole is a water course or siphon with branches that are still unexplored. A kind of leech was discovered in the pothole, which has been ascertained to represent a new species, genus and family; it has been named "Erpobdella mestrovi".
Gunung Mulu National Park
The national park has three notable caves: Sarawak Chamber, one of the world's largest underground chambers, Deer Cave, the largest cave passage in the world, and Clearwater Cave, the longest cave system in Southeast Asia. The Sarawak Chamber is long, wide and at least high, yielding a volume of and an unsupported roof span of . Meanwhile, the Deer Cave is at to in diameter. As of October 2018, Clearwater Cave has of explored passages.