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.
Yuanhui District is Luohe Municipal District, which is located in the central and southern part of Henan Province. Yuanghui District is the transportation hub of Henan Province, less than an hour's drive from Zhengzhou International Airport, 107 National Highway, Beijing-Guangzhou Railway, Beijing-Zhuhai Expressway running from the south to the north, Luobao and Luofu Railway, and Nanluo Expressway from east to west. Railways and expressways have a "double cross" structure. In 2012, the annual GDP of the Source and sink District reached 9.87633 billion yuan. In 2012, Yuanhui District has a total area of 201.6 square kilometers and a population of 320000. It has jurisdiction over 3 towns, 4 streets, one township, 109 administrative villages and 18 urban communities. It is the commercial, cultural and economic center of Luohe City.