From December of 2008, to January of 2009, an expedition of 16 people visited the second deepest cave on Earth, the Illyuzia-Mezhonnogo-Snezhnaya system. They have choosen the highest entrance to enter, and their plan was to explore the bottom of the cave (-1750m,15km+). Because of high level of water, and the big horizontal distance in difficult passages, and the need to repair the rigging it was 13 days to get to the bottom, where they spent 7 days with exploring, which led to the discovery of a more than 300m long hall (the longest one in the cave) by digging, and some other blind passages by climbing, all at the bottom area. In the end of the giant hall, a meander is starting, with one branch ending in a siphon, other branch not fully explored yet… there is still depth potential left. They spent the new year in the “Hall X”, which is another giant room (250m long) at the bottom, with celebration, fireworks, dancing, and singing the national anthems of 3 nations (Ukraine,Russia,Bulgaria). To get to the surface it was 5 days again, and they had another extra day, because the helicopter had to wait for the terrible weather to get better. They spent 26 days underground. The complete report, and a tons of quality pictures from this extraordinary expeditions can be found here.