Macau is an autonomous territory on the western side of the Pearl River Delta in East Asia. Macau is bordered by the city of Zhuhai in Mainland China to the north and the Pearl River Estuary to the east and south. Hong Kong lies about 64 kilometers (40 mi) to its east across the Delta. With a population of 650,900 living in an area of 30.5 km2 (11.8 sq. mi), it is the most densely populated region in the world.