箭扣 (箭釦) jiànkòu

jiànkòu proper noun Great Wall at Jiankou
Domain: History 历史 , Subdomain: China , Concept: Historical Sites and Scenic Places 名胜古迹
Notes: A section of the Great Wall located in Badaohe Village, Huairou County in Beijing. The Mutianyu section of the Great Wall is located to the east and Dazhenyu to the west.