In the mountains of Sichuan, China, lies a mysterious ancient city that was consigned to oblivion until the chance discovery of a jade object in 1927. Since that first find, over 10,000 artefacts made of gold, jade, ivory and bronze have been unearthed, buried by the inhabitants in sacrificial pits before they left the city about 3,000 years ago. The finds include objects unlike any other: curiously shaped bronze heads and masks covered in gold foil.