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.
Mei County, which belongs to Baoji City, Shaanxi Province, is called "Mei Wu" in ancient times. It is located at the foot of Taibai Mountain, the main peak of the Qinling Mountains, and crosses the Weihe River in the north. It is between 107 °39km east longitude and 108o 00km east longitude, and 334 °19' north latitude, with a total area of 863 square kilometers. Meixian County is one of the birthplaces of Western Zhou culture. Heavy national treasures such as Western Zhou bronzes and warring States bells have been unearthed many times. 27 Western Zhou bronzes unearthed in 2003 are known as major archaeological discoveries in the 21st century. Meixian is the hometown of celebrities such as Bai Qi, a general of the pre-Qin Dynasty, a famous official of the Shu Han Dynasty in the three Kingdoms, Wang Tao, a medical scientist in the Tang Dynasty, Zhang Zai, an ideologist in the Song Dynasty (because his theory was founded in Guanzhong, also known as Guanxue), and the Republic General Li Da. In 2018, Meixian County has jurisdiction over 1 street, 7 towns, 1 tourist area and 1 forest.