Farmers digging a well in a field approximately 20 miles east of Xi’an stumbled upon a pit containing 6,000 life-size terra cotta statues in March 1974. The site was soon identified as the burial place of Emperor Qin, and excavations began almost immediately. Historians now believe that some 700,000 workers worked for nearly three decades on the mausoleum.

So far, archaeologists have uncovered a 20-square-mile compound, including some 8,000 terra cotta soldiers, along with numerous horses and chariots, a pyramid mound marking the emperor’s tomb, remains of a palace, offices, store houses and stables. In addition to the large pit containing the 6,000 soldiers, a second pit was found with cavalry and infantry units and a third containing high-ranking officers and chariots. A fourth pit remained empty, suggesting that the burial pit was left unfinished at the time the emperor died.

After a 200-year period of provincial conflict called the Warring States Period, Qin Shi Huang is credited with unifying the provinces under one centralized government and establishing the capital at Xianyang. The stability of his rule enabled China to experience great advances in politics, economy and culture, including the introduction of a standard written script, a system of canals and roads, advances in metallurgy, standardized weights and measures and large-scale public works projects like the early Great Wall.

However, Qin was also known for his brutishness: He ordered the killings of scholars whose ideas he opposed, and showed little regard for the life of the conscripts who built those public works projects, including his burial complex. Numerous laborers and artisans lost their lives during its construction, while others were reportedly killed in order to preserve the secrecy of the tomb’s location and the treasures buried within.

The army of life-size terra cotta soldiers, archers, horses and chariots was stationed in military formation near Emperor Qin’s tomb in order to protect the emperor in the afterlife. The painstaking restoration of the figures—many of which were apparently vandalized soon after the emperor’s death—revealed that they were creating using molds and an early assembly-line-type construction.

Though most of their hands are identical, and only eight molds were used to shape their heads, distinctive surface features were added with clay after assembly. As a result, each terra cotta soldier appears to be unique in its facial features, revealing a high level of craftsmanship and artistry.

During excavation of the pits containing the Terra Cotta Warriors, archaeologists have found some 40,000 bronze weapons, including battle axes, crossbows, arrowheads and spears. Even after more than 2,000 years, these weapons remained extremely well preserved thanks to protective chrome plating, a seemingly modern technique (first used in Germany in 1937 and the United States in 1950) that reveals the sophistication of ancient Chinese metallurgy.

Even 40 years after its discovery, less than 1 percent of Emperor Qin’s tomb has been excavated. Initial fears of damaging the corpse and the artifacts within the tomb later gave way to concerns about the potential safety hazards involved with excavation. According to an account by the first century B.C. Chinese historian Sima Qian, entitled “The Grand Scribe’s Records,” mercury streams were inlaid in the floor of Qin’s burial chamber to simulate local rivers running through his tomb.

In 2005, a team led by Chinese archaeologist Duan Chingbo tested 4,000 samples from the earthen burial mound for mercury; all came back highly positive. Given such historical and chemical evidence, debate continues over whether to excavate the tomb at all, and what methods should be used to best protect its contents as well as the people working at the site.