On a warm spring morning in 1984, Dong Yao-hui and his two young friends, Wu De-yu and Zhang Yuan-hua, pulled on military surplus backpacks and boots and set out on a hike along a stretch of the Great Wall of China.
Their walk began at Laolongtou - or the Old Dragon's Head - in Shanhai Pass, where what was once believed to be the easternmost stretch of the Wall reaches into the Bohai Sea. From there they forged westward toward the mountains of Hebei province and the vast Chinese territory stretching out beyond.
