Workers digging a well outside the city of Xi'an, China, in 1974 struck upon one of the greatest archaeological discoveries in the world: a life-size clay soldier poised for battle.

The diggers notified Chinese authorities, who dispatched government archaeologists to the site.

They found not one, but thousands of clay soldiers, each with unique facial expressions and positioned according to rank. And though largely gray today, patches of paint hint at once brightly colored clothes. Further excavations have revealed swords, arrow tips, and other weapons, many in pristine condition.

The soldiers are in trenchlike, underground corridors. In some of the corridors, clay horses are aligned four abreast; behind them are wooden chariots.

The terra-cotta army, as it is known, is part of