Zhangjiakou also known as Kalgan and several other names, is a prefecture-level city in northwestern Hebei province in Northern China, bordering Beijing to the southeast, Inner Mongolia to the north and west, and Shanxi to the southwest. By 2019, its population was 4,650,000 inhabitants on 36,861.56 square kilometres, divided into 17 Counties and Districts. The built-up area made of Qiaoxi, Qiaodong, Chongli, Xuanhua, Xiahuayuan Districts largely being conurbated had 1,500,000 inhabitants in 2019 on 1,412.7 km².
Since ancient times, Zhangjiakou has been a stronghold of military significance and vied for by multiple sides. Hence, Zhangjiakou is given the nickname the Northern Gate of Beijing. Due to its strategic position on several important transport arteries, it is a critical node for travel between Hebei and Inner Mongolia and connecting northwest China, Mongolia, and Beijing. Dajingmen, an important gate and junction of the Great Wall of China is located here.
In the south, Zhangjiakou is largely cultivated for agricultural use. In the north, Bashang is a part of the Mongolian plateau and dominated by grasslands.