What lies beneath

The ancient city of Jiaohe had archaeologists stumped. Why were the older relics found near the Earth's surface, while more recent artifacts were buried far below? Yu Fei of China Features explores the city that went underground.

Jiaohe was not built by piling bricks from the ground - up it was carved into the earth.

A bird's-eye view of the ancient ruins shows a huge aircraft-carrier shape almost surrounded by water.