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.
Yushan District, which belongs to Maanshan City, Anhui Province, is bordered by the Yangtze River to the west, facing Hexian County, Hanshan County and Zhengpu Port New area across the river, bordering Jiangning District of Nanjing City in the east, Dangtu County and Bowang District in the south and Huashan District in the north, with a total area of 173 square kilometers. Yushan District was founded in 1976, named after the Rain Mountain in the territory. Cai Shiji, the head of "Sanji of the Yangtze River", Taibailou, which is listed as "one Pavilion on the third floor of the Yangtze River", the Tomb of Zhu ran, one of the top ten archaeological discoveries in China in the 1980s, Lin Sanzhi Art Museum of "Contemporary Caosheng", the ancient temple Lin Guangji Temple, Xiao Jiuhua, the ancient human site Yandun Mountain and other important cultural and tourism resources gather Yushan. City Grand Theater, Library, Museum, Science and Technology Museum, Planning Museum and many other cultural facilities, Anhui University of Technology, Wentian College of Hehai University, Ma saddle