The unopened tomb of Qin Shi Huang

The terracotta army, eight thousand individually-faced soldiers, is only the outer guard. The burial mound of China’s first emperor sits nearby and has never been opened. Sima Qian, writing a century later, describes a subterranean palace with rivers and a sea of flowing mercury and crossbows set to fire on intruders. Soil surveys across the mound have repeatedly found mercury concentrations far above background, in a pattern some read as matching China’s rivers. China has deliberately left it sealed, largely because excavation would likely destroy what is inside. UNESCO World Heritage.