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.
Phong Nha-Kẻ Bàng National Park
Sơn Đoòng Cave (in Vietnamese: Hang Sơn Đoòng, meaning Mountain River Cave) is a relatively recently discovered cave in the national park. Found by a local man and explored and publicly announced by the British cave scientists of the British Cave Research Association, it is regarded as the largest cave in the world. The biggest chamber of Sơn Đoòng is over five kilometers in length, 200 meters high and 150 meters wide. With these tremendous dimensions, Sơn Đoòng overtakes Deer Cave of Malaysia to take the title of world's largest cave. Because the fast flowing underground river in the cave deterred the explorers from going farther, they were only able to estimate the length of the cave using a flashlight.