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.
Xiangcheng District, under the jurisdiction of Suzhou City, Jiangsu Province, is located in the center of Suzhou. Xiangcheng District is located in the southeast of Jiangsu Province, China, with Yangcheng Lake and Kunshan to the east, Taihu Lake to the west, Wuxi and Changshu to the north, Suzhou Ancient City, Suzhou Industrial Park and High-tech Zone to the south. As of July 2018, Xiangcheng District has jurisdiction over 4 towns, 4 streets, 1 provincial economic development zone, 1 high-speed rail new town and 1 tourist resort: economic Development Zone, Yangcheng Lake tourist Resort, Yuanhe Street, Beiqiao Street, Taiping Street, Huangqiao Street, Weitang Town, Yangcheng Lake Town, Huangdai Town and Wangting Town. Xiangcheng District has 3 expressways and 14 crossings, such as Beijing, Shanghai and Sujiahang. It is one of the most important transportation hubs in the Yangtze River Delta. It has a total area of nearly 490 square kilometers and a population of nearly one million, including permanent residents.