Guangzhou, also known as Canton and alternately romanized as Kwangchow, is the capital and most populous city of the province of Guangdong in southern China. Located on the Pearl River about 120 km north-northwest of Hong Kong and 145 km north of Macau, Guangzhou has a history of over 2,200 years and was a major terminus of the maritime Silk Road, and continues to serve as a major port and transportation hub, as well as one of China's three largest cities. Long the only Chinese port accessible to most foreign traders, Guangzhou was captured by the British during the First Opium War. No longer enjoying a monopoly after the war, it lost trade to other ports such as Hong Kong and Shanghai, but continued to serve as a major transshipment port. Due to a high urban population and large volumes of port traffic, Guangzhou is classified as a Large-Port Megacity, the largest type of port-city in the world.