Great Wall of China at Mutianyu

26. Guard Tower on Spur

There are 22 watch towers distributed at close intervals along the wall. They are located not only in the main wall but also at the distinctive 'branch cities'. Branch cities are built on the hill ridge against the inner or outer side of the wall. They measure from several yards to dozens of yards across. On the northwest over 3,281-feet hills, lies a section of the wall called 'Ox Horn Edge.'