Shanghai is located on the Yangtze Estuary of China's east coast, with the Yangtze River to the north and Hangzhou Bay to the south. The land is formed by the Yangtze's natural deposition and modern land reclamation projects. As such, it has sandy soil, and skyscrapers are to be built with deep concrete piles to avoid sinking into the soft ground. The provincial-level Municipality of Shanghai administers both the estuary and many of its surrounding islands. It is roughly equidistant from Beijing and Guangzhou, bordering the East China Sea to the east, Zhejiang to the south, and Jiangsu to the west and north. The municipality's northernmost point is on Chongming Island, which is the second-largest island in mainland China after its expansion during the 20th century. It does not administratively include an exclave of Jiangsu on northern Chongming or the two islands forming Shanghai's Yangshan Port, which are parts of Zhejiang's Shengsi County.