A mesa is an isolated, flat-topped elevation, ridge or hill, which is bounded from all sides by steep escarpments and stands distinctly above a surrounding plain. Mesas characteristically consist of flat-lying soft sedimentary rocks capped by a more resistant layer or layers of harder rock, e.g. shales overlain by sandstones. The resistant layer acts as a caprock that forms the flat summit of a mesa. The caprock can consist of either sedimentary rocks such as sandstone and limestone; dissected lava flows; or a deeply eroded duricrust. Unlike plateau, whose usage does not imply horizontal layers of bedrock, e.g. Tibetan Plateau, the term mesa applies exclusively to the landforms built of flat-lying strata. Instead, flat-topped plateaus are specifically known as tablelands.
Chenggu County, belonging to Hanzhong City, Shaanxi Province, is located in the hinterland of Hanzhong Basin in southern Shaanxi, with the southern foot of Qinling Mountains to the north, the northern slope of Nanpingba Mountain to the north, and the Hanjiang River in Zhongna to the north. Between longitude 107 °30 'east longitude and 32 °45km north latitude, the terrain is north-south long (average length 101km), east-west narrow (average length 42km), with a total area of 2265 square kilometers. Chenggu, which has been established under the county system in the Qin Dynasty for more than 2300 years, is a "famous historical and cultural city" in Shaanxi Province. It is the life and burial place of Li Gu, a famous diplomat, explorer and pioneer of the Silk Road in the Western Han Dynasty, who is known as quot;, the mouthpiece of quot; Beidou. There are 437 scenic spots, cultural landscapes and cultural sites in the territory, including Tibetan.