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".
Levan Maruashvili
Levan Iosifovich Maruashvili ( born 25 October 1912, Novocherkassk, Russian Empire, — 5 December 1992, Tbilisi, Georgia) was a prominent Georgian geographer. Doctor of Geographical Sciences (1954), professor (1965). Honored Scientist of the Georgian SSR (1966) and Abkhaz ASSR. Honorary member of the Russian Geographical Society (1985). He introduced a new concept of karst-sphere into the science. Krubera Cave, which is the world’s deepest known cave (2197 m), was discovered by the Georgian researchers in 1960 by the leadership of Professor Levan Maruashvili.