Prayer Flags at the lake Nam Tso, the central Tibet area. Namtso Lake Nam or (officially, Nam Co; in Mongolian: Tengri Nor, literally "heavenly lake") is a great mountain salt lake in China, one of the most famous lakes of the Tibetan sacred lakes, located on the border between Damxung County, the (Lhasa Prefecture) and the District of Baingoin Nagqu Prefecture in the Tibet Autonomous Region, about 112 km NNW of the city of Lhasa. It is a sacred place of Tibetan Buddhism and many worshipers gather around the lake for a great ceremony that takes place the year of the sheep, every 12 years. In the extreme southeast is the Tashi Dor monastery.