The Jiankou Great Wall (Arrow Lock) is located in Huairou County,   It connects with the Mutianyu Great Wall 10 km to the east, 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 dangerous sections of the entire Great Wall.Make sure you wear footwear with very good grip and never attempt to traverse this section in the rain,particularly during thunderstorms.When the weather is fine,the Jiankou area offers fabulous opportunities to hike the Wall.