Macau, also spelled Macao, officially the Macao Special Administrative Region of the Peoples Republic of China, 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 to its east across the Delta. living in an area of, it is the most densely populated region in the world. Macau was administered by the Portuguese Empire and its inheritor states from the mid-16th century until late 1999, when it constituted the last remaining European colony in Asia. Under the policy of "one country, two systems", the State Council of the Peoples Republic of China is responsible for military defense and foreign affairs while Macau maintains its own legal system, public security force, monetary system, customs policy, and immigration policy. Macau participates in international organizations and events that do not require members to possess national sovereignty. Macau is a resort city in Southern China, known for its casinos and luxury hotels. Its gaming revenue has been the worlds largest since 2006, with the economy heavily dependent on gaming and tourism. According to The World Factbook, Macau has the fourth highest life expectancy in the world. Macau is among the worlds richest regions, and its GDP per capita by purchasing power parity is higher than that of any country in the world, according to the World Bank. It is widely known as the pre-eminent gambling capital of the world, greatly dwarfing other gambling centers/cities.