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.
Sihong County, under the jurisdiction of Suqian City, Jiangsu Province, is located in the northwest of Jiangsu Province, the lower reaches of the Huaihe River, Hongze Lake to the east and Anhui to the west, located in the cross-radiation area of the Yangtze River Delta Economic Zone and the Huaihe River eco-economic belt, with an administrative area of 2731 square kilometers and a population of 1.1 million. It is the hometown of famous wine, crab and eco-tourism in China. Sihong is the wine capital of China. Shuanggou Daqu, one of the top ten famous wines, is produced here. Sihong sits on 40% of the water surface of Hongze Lake, one of the four major freshwater lakes in China, and is embedded in the national Hongze Lake Wetland Park. Sihong gave birth to an ancient civilization. Fifty thousand years ago, the people of Xiacaowan lived here after the water and thrived. It is one of the centers of biological evolution in the Cenozoic world, and it is also one of the centers of human origin.