燕山

East-west range along northern Hebei and the top of Beijing Municipality. Carries long stretches of the Great Wall (Badaling 八达岭, Jinshanling 金山岭, Simatai 司马台 all lie on it) and historically defined the frontier between Han-Chinese agriculture and the northern steppe. Name comes from the ancient state of Yan (燕). Read first-tone Yān — do not confuse with 燕子 yànzi (swallow).

燕 has two readings: Yān (first tone, the Yan state / Yan Mountains / Beijing's old name 燕京) and yàn (fourth tone, swallow). Mountain/place name = Yān.