'south of Mount Heng') is a county and the 5th most populous county-level division in the Province of Hunan, China; it is under the administration of Hengyang prefecture-level city.

Its terrain is high in the northwest and low in the southeast, with hills and plains staggered.

Mineral deposits in the county are placer gold, ceramic mud, coal, kaolin, limestone, barite, lead, and zinc.

The layers of tertiary red rock are deposited in the basin's center and are about 3,000 meters thick.

A series of tenia fornices on the east, north, and west sides are centered around the central-south red basin, which has different structures.