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.
Ellison's Cave
Ellison's features a number of underground vertical pitches including the two deepest pits in the continental United States: Fantastic (586 feet) and Incredible (440 feet). These two pits lie on opposite sides of the cave. Nearby and parallel to Fantastic are Smokey I (500 feet), Smokey II (262 feet), and other extremely deep pitches. There are over 7 routes to reach the bottom level of the cave from the Fantastic side. Fantastic and Smokey I both extend to TAG Hall, a passage at the bottom of the cave. To reach Fantastic, or the large pits on the Fantastic side, cavers must also descend the Warm Up pit (125 feet).