the range rises between the chaobai river on the west and the shanhai pass on the east. it is made up mostly of limestone, granite, and basalt. its altitude ranges from 400 to 1000 meters. the main peak, mount wuling, is above sea level and is located in xinglong county in hebei. the range contains many narrow passes, such as the gubei pass, the xifeng pass, and the leng pass. the eastern stretch of the great wall of china, including badaling in northern beijing, can be found in the yan mountains. the mountains are also an important traffic gateway between north and south.