In 1973, three maps painted on silk were unearthed in Mawangdui No.3 tomb in Changsha, Hunan Province, namely, "topographic map", "garrison map" and "city map", but the name, scale and drawing time were not noted. According to this, the wooden slips buried with the tomb should be buried in the twelfth year (the first 168 years) of Emperor Wen of the Han Dynasty, which has been more than 21 years.