On March 29, 1974, farmers drilling a well 25 kilometres from Xian unearthed fragments of pottery. They had stumbled across the Terracotta Army, thousands of sculptures depicting the armies of Qin Shi Huang, China's first emperor. Their purpose was to protect the emperor in the afterlife and they were buried with him between 210 and 209BC. Here we take an in-depth look at this incredible archaeological discovery