At the foot of China’s Lishan Mountains lies one of the greatest archaeological discoveries of the modern era: an underground complex built to serve as the tomb of Qin Shi Huang, the first emperor of a unified China. To prepare for the afterlife, he mobilized a staggering 700,000 workers to construct a sprawling necropolis unlike anything the world had seen. Among its most astonishing features is an army of life-sized terra cotta soldiers—each one unique—tasked with protecting the emperor in death. Here are five facts about the site, now recognized as one of the Seven Wonders of the World.