Lake Dai

Lake Dai, also known by its Chinese name Daihai, is a lake in Liangcheng County, Ulanqab Prefecture, Inner Mongolia, China.

Geography
Lake Dai is a round lake with an area of about 160 km2, measuring about 25 km from east to west and about 20 km from north to south. It has an average depth of about 9 m and a maximal depth of 15 - 18 m.

History
Under the Qin, Huangqi and Dai lakes formed the northern boundaries of Yanmen Commandery, marking part of the northern frontier of the Chinese empire.