Ningbo is a sub-provincial city in northeast Zhejiang province, People's Republic of China. It comprises six urban districts, two satellite county-level cities, and two rural counties, including several islands in Hangzhou Bay and the East China Sea. Ningbo is the southern economic center of the Yangtze Delta megalopolis. The port of Ningbo–Zhoushan, spread across several locations, is the world's busiest port by cargo tonnage and world's third-busiest container port since 2010.