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
Chevé Cave was discovered in the mid-1980s by Bill Farr and Carol Vesely. Since then it has been pushed to the depth of , making it the second deepest cave in the Americas. The cave system has the greatest proven depth potential in the world as proven by a dye trace from its main entrance to the resurgence 2547 meters lower. The current terminus of the main Chevé system is a large breakdown pile reached after diving through two sumps. It is just over 9 kilometers from the entrance, making it currently one of the most remote underground locations on earth. Due to the logistical difficulties of continuing exploration from this point, current expeditions are focusing on finding mid-way entrances that might provide a quicker route into the middle Chevé system.