Qingdao is an important port and economic center of northern China. At the same time, it is one of the 14 open coastal cities in China and is an important foreign trade port. Qingdao has a total area of 10,654 square kilometers and a total population of 9.0462 million, including 1,159 square kilometers in the urban area and a population of 4.8759 million up to the end of 2014. Qingdao is divided into 10 county-level districts including Shibei, Licang, Laoshan, Chengyang and Huangdao etc. Qingdao is an important international trading port and maritime transportation hub along the Yellow River Basin and the West Bank of the Pacific Rim. It has trade with more than 450 ports in more than 130 countries and regions in the world, and its port throughput ranks among the top 10 in the world. Qingdao Airport is also one of the busiest airports in Shandong Province and even in the country. It has opened a number of international(regional) passenger and cargo routes and is open to navigation with 47 large and medium-sized cities in China. In terms of urban construction, Qingdao plans to build 18 rail transit lines. The currently opened lines 2, 3, and 11 have basically covered the five districts of the main city, with a total mileage of about 104.8 kilometers; Qingdao has a number of well-known office projects, such Shangshi Center, Shangri-La Center, HNA Center, Cosco Plaza, Excellence Century Center,etc..