Zhangjiakou (/ˈdʒɑːŋˈdʒjɑːˈkoʊ/), also known by 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. At the 2010 census, its population was 4,345,485 inhabitants on 36,861.56 square kilometres (14,232.33 sq mi), divided into 17 Counties and Districts. The built-up (or metro) area made of Qiaoxi, Qiaodong Districts and Wanquan County largely being conurbated had 838,978 inhabitants in 2010 on 1412.7 km².