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.
Tears of the Turtle Cave
Tears of the Turtle Cave is located in the Bob Marshall Wilderness in western Montana and is currently the deepest limestone cave in the United States since passing New Mexico's Lechuguilla cave in 2014. As of August 2016 the cave is known to be 1659 feet deep and 1.32 miles long. The cave consists mostly of roughly 2 foot wide fissure passage passing over dozens of short rope drops. With a mean temperature of 39 degrees F (4 C), it is muddy and poorly decorated.