The mountains north of Beijing including Badaling, Jundu Mountains and Fenghuanling all belong to the Yanshan range, which runs east-west, across northern Hebei Province. Yanshan separates the North China Plain from the steppes and held considerable military significance in history. All of Beijing's Great Wall sections were built in the Yanshan range, which reaches a height of at Haituoshan on the border between Yanqing County and Hebei.