Most of It Is Ming

The Ming rebuild was a desperate project. After decades of raids by Mongol cavalry, the Ming poured massive resources into stone and brick walls totaling more than 5,500 miles. Watchtowers stood every 100 to 200 meters, backed by signal towers and garrison forts — the largest defensive construction in human history.

And it largely failed. The Manchus who conquered Ming China in 1644 did not breach the wall. A monument built to keep empires out could not survive a single act of betrayal from within.