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.
Dangshan, which belongs to Suzhou City, Anhui Province, is called Xiayi in ancient times. It is located at the northernmost end of Anhui Province, at the junction of Anhui, Jiangsu, Shandong and Henan provinces and seven counties, and is connected to Xiao County of this province in the southeast. It is adjacent to Yongcheng City, Xiayi County and Yucheng County of Henan Province from south to west; it is connected with Shan County of Shandong Province in the northwest and Feng County of Jiangsu Province in the northeast. The total area is 1193 square kilometers. Dangshan has a long history and rich resources. It has been built for more than 2200 years since Xiayi County was built in Qin Dynasty. Dangshan is known as the "pear capital of the world" and is known as "the hometown of crisp pears in China". In April 2010, it was recognized by Guinness Book of Records as the largest continuous orchard production area in the world. It is "the hometown of Chinese martial arts" and "the hometown of Chinese suona". It is the hometown of Zhu Wen, the founding emperor of the later Liang Dynasty. By 2018, there were 13 towns under the jurisdiction of Dangshan County.