The Jiankou Great Wall (Arrow Lock) is located in Huairou County, 73 km north from Beijing City. It connects with the Mutianyu Great Wall 10 km to the east, and with the Huanghuacheng Great Wall to the west. This section was built in 1368 during the period of the Ming Dynasty.It is built of large white hill rocks which makes it very prominent from a distance. The major section of this Great Wall is built along a mountain ridge with tall cliffs on each side, and as a result of the lack of repairs, it is now one of the most dangerous sections of the entire Great Wall. [China.org.cn]