There is no Daihai Lake in Liangcheng County, Wulanchabu City, which was called Tianchi in ancient times and is the third largest inland lake in the autonomous region. The water surface of Daihai Lake is about 130 square kilometers, and it has the reputation of "Tianchi Lake on the grassland". Daihai was called Zhu in the Han Dynasty, Huluhai in the Northern Wei Dynasty, Yuanyang Garden in the Song and Yuan Dynasties, Daigen Tara in the Qing Dynasty, and Daihai is still in use today. Its water source consists of more than 20 surrounding rivers and middle groundwater. The shape of Daihai Lake is irregular, between rectangle and ellipse. Lake area 160 km2, without islands. The bottom of the lake is an asymmetric basin, with the deepest part leaning to the northeast, flat basin bottom and steep nearshore zone. The bottom line descends smoothly from the coastline to the deepest part, and there are no irregular shapes such as ups and downs and scarps. The north shore line is steepest, the west coast line is slowest, and the east coast and south coast are in between.