Shanghai (/ʃæŋˈhaɪ/;[17] Chinese: 上海, Shanghainese pronunciation [zɑ̃̀.hɛ́] (listen), Standard Mandarin pronunciation: [ʂâŋ.xàɪ] (listen)) is one of the four direct-administered municipalities of the People's Republic of China.[a] The city is located on the southern estuary of the Yangtze River, with the Huangpu River flowing through it. With a population of 24.89 million as of 2021, Shanghai is the most populous urban area in China and the most populous city proper in the world. It is the only city in East Asia with a GDP greater than its corresponding capital. As of 2018, the Greater Shanghai metropolitan area, which includes Suzhou, Wuxi, Nantong, Ningbo, Jiaxing, Zhoushan, and Huzhou, was estimated to produce a gross metropolitan product (nominal) of nearly 9.1 trillion RMB ($1.33 trillion).[20] Shanghai has been one of the world's major centers for finance, business and economics, research, education, science and technology, manufacturing, tourism, culture, dining, art, fashion, sports, and transportation, and the Port of Shanghai is the world's busiest container port. In 2019, the Shanghai Pudong International Airport was one of the world's 10 busiest airports by passenger traffic,[21][22] and one of the two international airports serving the Shanghai metropolitan area, the other one being the Shanghai Hongqiao International Airport.