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.
Thiên Đường Cave
Thiên Đường Cave (Paradise Cave) is a cave in Phong Nha-Kẻ Bàng National Park, UNESCO's World Heritage Site, 60 km northwest of Đồng Hới city.
Thiên Đường Cave is located on an elevation of 200 meters above the sea level, near the west branch of Ho Chi Minh Highway, in Son Trach Commune, Bố Trạch District, Quảng Bình Province, Vietnam. The cave was discovered by a local man in 2005 and the first 5 km of this cave was explored by explorers from British Cave Research Association in 2005, the whole 31 km was explored and publicly announced by the British cave explorers. This cave is 31 km long, longer than Phong Nha Cave which had been considered the longest cave in this national park. The height can reach to 72 m and 150 m wide. The limestone formation is also more spectacular than that of Phong Nha Cave. The British cave explorers were impressed by the beautiful and spectacular stalactites and stalagmites inside this cave and they named it "Thiên Đường Cave" ("Paradise Cave").
In 2012, a new species of troglobiontic scorpion species, "Vietbocap thienduongensis" was found in here.