Hong Kong, officially Hong Kong Special Administrative Region of the People's Republic of China, is an autonomous territory on the southern coast of China at the Pearl River Estuary of the South China Sea. Hong Kong is known for its skyline and deep natural harbour. It has a total land and sea area of 2,754 km2 and shares its northern border with the Guangdong Province of Mainland China. With 7.2 million residents of various nationalities, Hong Kong is the world's fourth most densely populated sovereign state or territory.