Chongming Island lies against the northern shore of the Yangtze River and is an alluvial island formed by silt carried along the river. It gives the name to Chongming County, the only county of Shanghai. It is the third largest island in greater China at
1,041.21 km2 (402.01 sq mi), and is the second largest
after Hainan Island currently under the administration of the People's Republic of China. The other two inhabited Shanghai islands are Changxing Island at
88.54 km2 (34.19 sq mi), and Hengsha Island at 55.74 km2 (21.52 sq mi). The 25.5 km (15.8 mi) Shanghai Yangtze River Tunnel and Bridge joining the island to Shanghai opened on 2009-10-31 The island will be connected to Jiangsu Province via Chonghai Bridge which has not been built yet and Chongqi Bridge which have be finished last year (2011).