Beijing, previously romanized as Peking, is the capital city of China. With more than 22 million residents, it is the world's most populous national capital city, as well as China's second largest city by urban area, after Shanghai. It is located in Northern China, and is governed as a municipality under the direct administration of the State Council with 16 urban districts. Beijing is mostly surrounded by Hebei Province and neighbors Tianjin to the southeast; together, the three divisions form the Jing-Jin-Ji cluster. Beijing is a global city and one of the world's leading centres for culture, diplomacy, politics, finance, business and economics, education, research, language, tourism, media, sport, science and technology, transportation, and art. It is home to the headquarters of most of China's largest state-owned companies and houses the largest number of Fortune Global 500 companies in the world, as well as the world's four biggest financial institutions by total assets. It is also a major hub for the national highway, expressway, railway, and high-speed rail networks. For a decade before the COVID-19 pandemic, Beijing Capital International Airport was Asia's busiest airport (2009–2019) and the second busiest airport in the world (2010–2019). In 2020, the Beijing subway was the fourth busiest and second longest in the world. Beijing Daxing International Airport, Beijing's second international airport, is the largest single-structure airport terminal in the world.