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.
Langao County, which belongs to Ankang City, Shaanxi Province, is located in southern Shaanxi, at the northern foot of Dabashan Mountain, bordering Chengkou County of Chongqing City in the south, Hanbin District of Ankang City in the north, Ziyang County in the west and Pingli County in the east, with a maximum elevation of 2641 meters and a minimum elevation of 331m. It covers an area of 1956 square kilometers, with a total population of 168200 (2017). Langao Nangong rice field was selected as "China's beautiful countryside, 2012 China's best leisure town, one of the most beautiful cities in China." Langao County was founded in the Qing Dynasty, there are Nangongshan, Lanhe rafting and other scenic spots, known as the hometown of Chinese konjac. In 2013, the GDP of Langao County reached 3.1 billion yuan, an increase of 14% over 2012. On February 2, 2019, by the State Administration of traditional Chinese Medicine