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.
Tham Phra Wang Daeng
Tham Phra Wang Daeng, also known as the Cave of the Monk (), is a deep cave located in Thung Salaeng Luang National Park, Amphoe Noen Maprang, Phitsanulok Province, upper central Thailand. It is the longest cave in Thailand, the distance is about 13 kilometers. Buddhist statues and relics, carvings and reliefs, a subterranean river, multiple bat colonies, and a trove of speleothems populate the cave. In 2003, a biological expedition to the cave resulted in the discovery of new fish species, including discoveries in the Balitoridae and Cyprinidae families.