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.
Yanta District is the largest core area in the central city of Xi'an, the economic and cultural center of the province, located in the Nancheng plate of Xi'an City, Shaanxi Province. There are two state-level economic development zones, Xi'an High-tech Industrial Development Zone and Qujiang New area, with a total area of 152square kilometers, 10 subdistrict offices and a resident population of 1.2311 million (2017). It is named because of the world-famous historical and cultural heritage Dayan Pagoda in the area. Yanta District is a leading strong economic area in central and western China. It is a famous commercial and scientific and educational district in China. Its total economic output exceeded 152.1 billion RMB and per capita GDP exceeded 21300 US dollars in 2017. China's top 100 urban areas ranked 29th and all ranked first in western China. It is the first comprehensive municipal district in western China and the largest economy in Xi'an.