Blue Lake is located in Aldarkhan sum of Zavkhan Aimag. The lake, called Otgon Lake, is placed at 2450 meters of altitude in the heart of Dayan Mounain, at the northwest of Otgontenger Mountain. It is the freshest mild lake created by ancient glaciers and is 5.4 km long and covers an area of 11 squares km. The length of its coastline is 14.5 km, its depth is 4.5 meters and has a volume of 17.7 million cubic meters with a flat bottom.  

The lake freezes from October to May and its water erythrocytes are low, around 62.4 mg, and contains chemical elements like sodium, calcium, magnesium etc… Several ponds join into this lake and is fed by black sediment ground water.