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San Francisco (/ˌsæn frənˈsɪskoʊ/; Spanish for "Saint Francis"), officially the City and County of San Francisco, is the commercial, financial, and cultural center of Northern California in the United States. The city proper is the fourth most populous in California and 17th most populous in the United States, with 815,201 residents as of 2021. It covers a land area of 46.9 square miles (121 square kilometers), at the end of the San Francisco Peninsula, making it the second most densely populated large U.S. city after New York City, and the fifth most densely populated U.S. county, behind only four of the five New York City boroughs. Among the 91 U.S. cities proper with over 250,000 residents, San Francisco was ranked first by per capita income (at $160,749) and sixth by aggregate income as of 2021. Colloquial nicknames for San Francisco include SF, San Fran, The City, Frisco, and Baghdad by the Bay.

San Francisco and the surrounding San Francisco Bay Area are a global center of economic activity and the arts and sciences, spurred by leading universities, high-tech, healthcare, FIRE, and professional services sectors. As of 2020, the metropolitan area, with 6.7 million residents, ranked 5th by GDP ($874 billion) and 2nd by GDP per capita ($131,082) across the OECD countries, ahead of global cities like Paris, London, and Singapore. San Francisco anchors the 13th most populous metropolitan statistical area in the United States with 4.6 million residents, and the fourth-largest by aggregate income and economic output, with a GDP of $669 billion in 2021. The wider San Jose–San Francisco–Oakland, CA Combined Statistical Area is the fifth most populous, with 9.5 million residents, and the third-largest by economic output, with a GDP of $1.25 trillion in 2021. In the same year, San Francisco proper had a GDP of $236.4 billion, and a GDP per capita of $289,990. San Francisco was ranked seventh in the world and third in the United States on the Global Financial Centres Index as of March 2022.

Haidian District, which belongs to Beijing, is located in the west and northwest of Beijing, adjacent to Xicheng District and Chaoyang District in the east, Fengtai District in the south, Shijingshan District and Mentougou District in the west, and Changping District in the north. It covers an area of 431 square kilometers, with a boundary line of about 146.2 kilometers, 30 kilometers from north to south, and 29 kilometers from east to west, accounting for about 2.6 percent of the total area of Beijing. The area is between 39 °53 degrees north latitude and 40 degrees 09 degrees north latitude and 116 degrees 23 'east longitude. In the early Yuan Dynasty, the town of Haidian was near a shallow lake, so it was called "Haidian", that is, Haidian today. In September 1952, Haidian District was officially named, and the area under its jurisdiction was formed in January 1963. As of 2018, Haidian District has jurisdiction over 22 streets and 7 districts. As of
Airport In Haidian - Beijing Capital International Airport
Beijing Capital International Airport (Beijing Capital International Airport, IATA: PEK, ICAO: ZBAA), located in the northeast suburb of Beijing, China, 25 kilometers southwest of Beijing city center, 67 kilometers south of Beijing Daxing International Airport, is a 4F international airport   , is one of the three major portal complex hubs in China   , members of the international air cargo hub group in the Bohai Rim region   , the world's largest airport   .
Beijing Capital International Airport was built in 1958. On January 1, 1980, supporting projects such as the T1 terminal building, the apron, and the parking lot in front of the building were completed and officially put into use. On November 1, 1999, the T2 terminal was officially put into use, and at the same time, the T1 terminal was closed for renovation. On September 20, 2004, the T1 terminal was put into use again. In the spring of 2008, the airport expansion project (Terminal T3) was completed.  
As of July 2017, Beijing Capital International Airport has three terminal buildings with a total area of ​​1.41 million square meters; there are two 4F runways and one 4E runway   The length and width are 3800×60 meters, 3200×50 meters, 3800 meters×60 meters respectively; there are 314 seats in total; 252 domestic and foreign routes have been opened.    
From 1978 to 2018, the annual passenger throughput of Beijing Capital International Airport increased from 1.03 million to 101 million, ranking first in Asia and second in the world.   In 2019, the passenger throughput of Beijing Capital International Airport was 100.013 million passengers, a year-on-year decrease of 1.0%; the cargo and mail throughput was 1.9553 million tons, a year-on-year decrease of 5.7%; , No. 2, No. 1.  
In 2021, Capital Airport will add three new domestic destinations, namely Huai'an, Tumusuk and Jingzhou   .
Travel Sights In Haidian
Travel Notes In Haidian
Travel Asks In Haidian
Travel Asks In Haidian