It is located in the middle south of Jiangsu Province and in the cradle of the Yangtze River. It is largely situated on the second biggest island in the Yangtze River, known locally as Yangzhong Island, which was formed about 300 years ago during a major flood event. It occupies an area of about 332 square kilometres. It is flat (with the exception of a man-made hill which is about 6 metres high) and has an elevation of two to three metres above the normal river level. It has a population of about 430,000 people which includes about 280,000 native residents and 150,000 immigrants. Bridges, ferries, and expressways link the island to the mainland, including the Yangzhong Yangtze River Bridge, the Second Yangzhong Yangtze River Bridge, the Yangzhong-Gaogang ferry, the Shanghai-Nanjing Expressway and the Beijing-Shanghai expressway.