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.
Huangling County, the site of the Yellow Emperor Mausoleum of Xuanyuan, the first ancestor of the Chinese nation, belongs to Yan'an City, Shaanxi Province. It is located in the middle of Shaanxi Province, south of Yan'an City, 124 kilometers north of Yan'an, and 165 kilometers south of Xi'an, the ancient capital. The total area is 2292 square kilometers. Huangling is rich in human resources. The mausoleum of the Yellow Emperor Xuanyuan, the first ancestor of the Chinese nation, is located at the top of Qiaoshan, 1 km north of the county seat. It is the first batch of national key cultural relic protection units announced by the State Council. It has the reputation of "the first tomb in the world". Huangling County is named as "the hometown of the sacrificial culture of the Yellow Emperor of China" and the first batch of strong tourist counties in Shaanxi Province. In 2018, Huangling County had jurisdiction over one street and five towns, with a resident population of 131900, achieving a regional gross domestic product (GDP) of 15.241 billion yuan, of which the primary industry increased.