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.
Chevé Cave
In 2004, an international caving expedition led by the U.S. Deep Caving Team discovered a new cave they named J2. The entrance of J2 located 5 kilometers northeast of the Chevé Cave entrance. J2 appears to head in the direction of Chevé Cave, with a predicted intersection beyond the tunnel collapse that stopped the team in 2003. Current expeditions are underway to find a connection between J2 and Chevé Cave, which will produce a cave system more than 2 kilometers in depth. The integration of the entire system will produce a 2,597 meter deep cave and would represent the deepest cave in the world.