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.
Indian Caverns
Indian Caverns was a show cave in Spruce Creek, Pennsylvania, United States from 1929-2017. It is a horizontal karst cave of Ordovician Nealmont/Benner limestone, estimated to be about 500,000 years old. It is the second-largest cave in Pennsylvania and the largest limestone cave. Indian Caverns consists of two sections, originally separated by a 14-foot wall: the "Historic Cave" and the "Giant's Hall". The "historic" part of the cave is generally low-ceilinged and closer to the surface (as shallow as 15 ft) with a couple of wide rooms and extensive speleothem formation. The Giant's Hall area consists of several large passageways, up to 60 feet high, but with fewer speleothems - though it does include the largest sheet of flowstone in the northeast and a substantial rimstone pool. The lowest point of the cave is approximately 140 feet beneath the surface and the cave temperature is a constant 56 degrees Fahrenheit (13 degrees Celsius).