Krubera Cave
The difference in elevation of the cave's entrance and its deepest explored point is . It became the deepest-known cave in the world in 2001 when the expedition of the Ukrainian Speleological Association reached a depth of which exceeded the depth of the previous deepest-known cave, Lamprechtsofen, in the Austrian Alps, by . In 2004, for the first time in the history of speleology, the Ukrainian Speleological Association expedition reached a depth greater than , and explored the cave to . Ukrainian diver Gennadiy Samokhin extended the cave by diving in the terminal sump to 46 metres' depth in 2007 and then to 52 m in 2012, setting successive world records of 2,191 m and 2,197 m, respectively. Krubera is one of the two known caves on Earth deeper than 2,000 metres.
Lazareva Pećina
The Lazareva Pećina, which translates Lazar's Cave, is the longest explored cave in Serbia. Located in Bor municipality, near Zlot, the cave is also sometimes referred to as Zlotska Cave. According to 2012's "Recent Landform Evolution: The Carpatho-Balkan-Dinaric Region", the cave is long. The cave is situated near the entrance of the deep canyon carved into the mountains by the river Zlotska.