In Rozanski kukovi, National park North Velebit, Croatia
Vertical pit named Divka Gromovnica (513 m)
Cave explorers from Velebit Speleological Society and other clubs from Croatia discovered a pit inside a mountain range in central Croatia believed to have the world's deepest subterranean vertical drop, at nearly 513 m. At the foot of the Velebita cave are small ponds and streams, including one of the largest known colonies of subterranean leeches. It is located in the rocky Velebit mountain range in central Croatia.
More info: Croatian Speleological Server