Macau, also spelled Macao, officially the Macao Special Administrative Region of the People's Republic of China, is a Special Administrative Region on the western side of the Pearl River Delta, China. Macau is also bordered by the city of Zhuhai of Guangdong Province, Mainland China to the North and the Pearl River Estuary to the East and South. Hong Kong lies about 64 kilometers to its East across the Delta.[6] With an estimated population of around 649,100 living in an area of 30.4 km2 (11.7 sq mi), it is the most densely populated region in the world.