Photos of ancient wall Beijing Knot

https://www.flickr.com/photos/erussell1984/4753642278/in/photolist-oJQCYp-eJiY5-bRfoPB-4c6en-vqxUv2-8f4EeC-fLiAjp-EP5VTf-doXCmV-fLiwq4-2S1185-2S11GJ-5aEZWg-81zoya-5yUDmF-2RZZBs-aoVxqW-5yVZ84-5iWPBM-9qWFBr-4bhZNa-4bi1Fg-4bi1qF-4bi1aX