Tianjin (pinyin: About this sound Tiānjīn), formerly known in English as Tientsin, is a metropolis in northern coastal Mainland China and one of the four national central cities of the country, with a total population of 15,469,500, and is also the world's 6th-most populous city proper. It is governed as one of the four direct-controlled municipalities of the PRC and is thus under direct administration of the central government. Tianjin borders Hebei Province and Beijing Municipality, bounded to the east by the Bohai Gulf portion of the Yellow Sea. Part of the Bohai Economic Rim, it is the largest coastal city in northern China.
In terms of urban population, Tianjin is the fourth largest in China, after Shanghai, Beijing, and Guangzhou. In terms of administrative area population, Tianjin ranks fifth in Mainland China. The walled city of Tianjin was built in 1404. As a treaty port since 1860, Tianjin has been a major seaport and gateway to Beijing. During the Boxer Rebellion the city was the seat of the Tianjin Provisional Government. Under the Qing dynasty and the Republic of China, Tianjin became one of the largest cities in the region. At that time, numerous European-style buildings and mansions were constructed in concessions, many of which are well-preserved today. After the founding of the People's Republic of China, Tianjin suffered a depression due to the policy of the central government and Tangshan earthquake, but recovered from 1990s. Nowadays Tianjin is a dual-core city, with its main urban area (including the old city) located along the Hai River, which connects to the Yellow and Yangtze Rivers via the Grand Canal; and Binhai, a New Area urban core located east of the old city, on the coast of Bohai Sea. As of the end of 2010, around 285 Fortune 500 companies have set up base in Binhai, which is a new growth pole in China and is a hub of advanced industry and financial activity.
The land where Tianjin is located today was created in ancient times by sedimentation of various rivers entering the sea at Bohai Gulf, including the Yellow River which entered the sea in this area at one point. Before this time, it was open sea.
The opening of the Grand Canal during the Sui dynasty prompted the development of Tianjin into a trading center.
Tianjin is located along the west coast of the Bohai Gulf, looking out to the provinces Shandong and Liaoning across those waters, bordered by Beijing 120 kilometres (75 mi) to the northwest, and except for the east, is surrounded on all sides by Hebei. With a latitude ranging from 38° 34' to 40° 15' N, and longitude ranging from 116° 43' to 118° 04' E, the total area is 11,860.63 square kilometres (4,579.41 square miles). There is 153 km (95 mi) of coastline and 1,137.48 kilometres (706.80 miles) of land border. It lies at the northern end of the Grand Canal of China, which connects with the Yellow River and Yangtze River. The municipality is generally flat, and swampy near the coast, but hilly in the far north, where the Yan Mountains intrude into northern Tianjin. The highest point in the municipality is Jiuding Peak (九顶山) in Ji County on the northern border with Hebei, at an altitude of 1,078.5 m (3,538 ft).
Tianjin features a four-season, monsoon-influenced climate, typical of East Asia, with cold, windy, very dry winters reflecting the influence of the vast Siberian anticyclone, and hot, humid summers, due to the monsoon. Spring in the city is dry and windy, occasionally seeing sandstorms blowing in from the Gobi Desert, capable of lasting for several days. The monthly 24-hour average temperature ranges from −3.4 °C (25.9 °F) in January to 26.8 °C (80.2 °F) in July, with an annual mean of 12.90 °C (55.2 °F). With monthly percent possible sunshine ranging from 48% in July to 61% in October, the city receives 2,522 hours of bright sunshine annually. Having a low annual total precipitation of 511 millimetres (20.1 in), and nearly three-fifths of it occurring in July and August alone, the city lies within the semi-arid zone, with parts of the municipality being humid continental (Köppen Dwa/BSk, respectively).
Extreme temperatures have ranged from −22.9 °C (−9 °F) to 40.5 °C (105 °F).