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.
Lianhu District (Lianhu District), the municipal district of Xi'an, is located in the northwest of Xi'an. To the east, North main Street, North Guanzheng Street and Longshou Village are bordered by Xincheng District, West Houhu Railway and North latitude 26 Street are connected with Weiyang District, and the moat and Great Ring River are adjacent to Beilin District and Yanta District in the south. The total area is 38 square kilometers and the total population is 712300 (2015). It has jurisdiction over 9 streets, and the district government is stationed at 159 Beiyuanmen Street. Lianhu District is the starting point of the famous "Silk Road" in history, with large-scale sculptures of "Silk Road", Datang West City, Datang West City Museum and other silk road tourist attractions. Traffic is developed, Longhai railway, Xihu railway transit, there are Huancheng Road, the second Ring Road and other street roads. The monuments are the site of Chang'an City in the Tang Dynasty, built in the Ming and Qing dynasties.