Zhangjiakou is a prefecture-level city in Hebei Province of North China. It has a population of 4.3 million, and covers 36,947 square kilometers.

　　Zhangjiakou was historically known to the Europeans as Kalgan until the mid 20th century. This name derives from the Mongolian name of the city, means "gate".

　　Zhangjiakou has been nicknamed "Beijing's Northern Door" due to its strategic location.

　　Geography and transport

　　The entire jurisdiction of Zhangjiakou City extends beyond just central Zhangjiakou (divided into Qiaoxi District and Qiaodong District), but extends also into other outlying areas such as Zhangbei, Yangyuan, Xuanhua and even Huailai County, which is less than 20 km away from Beijing.

　　The city lies in the northwestern corner of the province and is linked from Datong in Shanxi by the Xuanda Expressway and from Beijing by means of the Jingzhang Expressway. Zhangjiakou is further linked by a freeway to Inner Mongolia which opened on September 7, 2005.

　　View of Zhangjiakou (Kalgan) in 1698.The water-scarce city was historically the chief northern gate in the Great Wall to China for Europeans travelling along the Tea Road (such as Nicolae Milescu).

　　In August 1211, there raised the Badger's Mount Campaign, Genghis Khan command 90,000 Mongols destroyed 450,000 Jin Dynasty army.

　　In the 19th century, the town was the seat of a very extensive transit trade. In early autumn long lines of camels would come in from all quarters for the conveyance of the tea chests from Zhangjiakou, the Kalgan, to Kyakhta; and each caravan usually made three journeys in the winter. Some Russian merchants had permanent residences and warehouses just outside the gate.

　　In October 1909, Kalgan was connected by railway with Peking. The 1911 Encyclopaedia Britannica noted that, in Kalgan, "the ordinary houses have an unusual appearance, from the fact that they are mostly roofed with earth and become covered with green-sward" and that "on the way to Peking the road passes over a beautiful bridge of seven arches, ornamented with marble figures of animals".

　　In the early 1960s at the height of Sino-Soviet tensions, Zhangjiakou was considered one of the most important cities in China for military strategy reasons. Zhangjiakou was aptly nicknamed, "Beijing's Northern Door", because whoever controlled Zhangjiakou was in a good position to either attack (in the case of the Soviets) or defend (in the case of the Chinese) Beijing.

　　A corner in downtown Zhangjiakou.The vicinity of Zhangjiakou is rich in coal and iron ore, making it an ideal location for developing iron and steel industry. Apart from metallurgy, the city is home to one of China's most important grape wine industries, with the Great Wall Wine Company being located in Shacheng (沙城鎮(zhèn)), Huailai County.

　　Zhangjiakou is home to Hebei North University. University is prevaling its netwok internationally.Many foreign studients are now studing here.