Beijing is an important world capital and global power city, and one of the world's leading centers for politics, economy and business, finance, education, culture, innovation and technology, architecture, language, and diplomacy. A megacity, Beijing is the second largest Chinese city by urban population after Shanghai and is the nation's political, cultural, and educational center.
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.It is also a major hub for the national highway, expressway, railway, and high-speed rail networks. The Beijing Capital International Airport has been the second busiest in the world by passenger traffic since 2010, and, as of 2016, the city's subway network is the busiest and second longest in the world.
Combining both modern and traditional architecture, Beijing is one of the oldest cities in the world, with a rich history dating back three millennia. As the last of the Four Great Ancient Capitals of China, Beijing has been the political center of the country for most of the past eight centuries, and was the largest city in the world by population for much of the second millennium A.D.
Encyclopædia Britannica notes that "few cities in the world have served for so long as the political headquarters and cultural center of an area as immense as China." With mountains surrounding the inland city on three sides, in addition to the old inner and outer city walls, Beijing was strategically poised and developed to be the residence of the emperor and thus was the perfect location for the imperial capital.
The city is renowned for its opulent palaces, temples, parks, gardens, tombs, walls and gates. It has seven UNESCO World Heritage Sites—the Forbidden City, Temple of Heaven, Summer Palace, Ming Tombs, Zhoukoudian, and parts of the Great Wall and the Grand Canal— all tourist locations. Siheyuans, the city's traditional housing style, and hutongs, the narrow alleys between siheyuans, are major tourist attractions and are common in urban Beijing.