Krubera Cave, Russia

Krubera Cave (Georgian: კრუბერის გამოქვაბული; or Voronya Cave, sometimes spelled Voronja Cave) is the deepest-known cave onEarth. It is located in the Arabika Massif of the Gagra Range of the Western Caucasus, in the Gagra districtof Abkhazia, a breakaway region of Georgia. The difference in elevation of the cave's entrance and its deepest explored point is 2,197 ± 20 metres (7,208 ± 66 ft). It became the deepest-known cave in the world in 2001 when the expedition of theUkrainian Speleological Association reached a depth of 1,710 m (5,610 ft) which exceeded the depth of the previous deepest-known cave, Lamprechtsofen, in the Austrian Alps, by 80 metres (260 ft). In 2004, for the first time in the history of speleology, the Ukrainian Speleological Association expedition reached a depth greater than 2,000 metres (6,600 ft), and explored the cave to −2,080 m (−6,824 ft). Source: Wikipedia