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".
GB Cave
The cave was first entered on 19 November 1939, after ten months of digging, by the University of Bristol Spelæological Society, and was named in recognition of the two members, F. J. Goddard and C. C. Barker, who had done most of the work involved in its discovery. The cave is located within the Cheddar Complex and the 17-acre GB Gruffy nature reserve and is close to Charterhouse Cave, the deepest cave in the region.