Jiaohe Ancient City stands isolated on a 30-meter-high plateau in the Ya'ernaizi Valley, 10 kilometers east of Turpan. The whole city of Jiaohe Ancient City stretches about 1650 meters from south to north, and 300 meters from east to west. Historical records and excavation reveal evidence of a prosperous ancient trading center and military stronghold from 1,600 years ago. Owing to the arid climate and remote location, Jiaohe remains relatively intact, leaving us a rare example of an earthen castle, the largest, oldest and best-preserved earthen city in the world.[Photo/CFP]