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.
Dongguan, one of the prefecture-level cities under the jurisdiction of Guangdong Province, one of the central cities of the Pearl River Delta and one of the cities of Guangdong-Hong Kong-Macau Greater Bay Area, is a central city on the east coast of the Pearl River Delta approved by the State Council. By 2018, the city had jurisdiction over 4 streets and 28 towns, with a land area of 2460.1 square kilometers, a sea area of 82.57 square kilometers, a resident population of 8.3922 million, and an urban population of 7.6386 million, with an urbanization rate of 91.02%. Dongguan is located in the central and southern part of Guangdong Province, the east bank of the Pearl River Estuary, Guangzhou in the northwest, Shenzhen in the south and Huizhou in the northeast. Dongguan is the first of the "four little tigers of Guangdong" and is known as the "factory of the world". It is also one of the five prefecture-level cities without districts and one of the new first-tier cities in the country. Dongguan established a county during the period of the three Kingdoms.