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.
Sihui is a county-level city hosted by Zhaoqing City, Guangdong Province. Because of the place where the four rivers (Xijiang, Beijiang, Suijiang and Longjiang) will flow, it is named "Sihui". Located in the middle of Guangdong Province, east of Zhaoqing, the northwest edge of the Pearl River Delta, located in the lower reaches of the West, North and Suisanjiang River, the Tropic of Cancer divides the whole territory into two. It is bordered by Sanshui District of Foshan City in the east, Dinghu District of Zhaoqing City in the south, Guangning County in the northwest and Qingxin District of Qingyuan City in the northeast, which belongs to the Pearl River Delta Economic Zone. It entered the ranks of the top 100 counties (cities) in the rural economy and the top 100 counties (cities) in the country in 1993 and 1994 respectively, and achieved a well-off society in 1996. In 2014, Sihui City ranked 97th among the top 100 counties and cities with comprehensive strength of small and medium-sized cities in China and 100 small and medium-sized cities with the most investment potential in China.