The Ancient City of Jiaohe, also known as Ancient City on Ya'er Lake, is an ancient Chinese archaeological site found in the Yarnaz Valley, 10 km west of the city of Turpan, Xinjiang province. It was a prefecture of the Gaochang during the Sixteen States (304AD-439 AD) and a county of the Gaochang Prefecture after the 14th year (640 AD) of the Zhenguan reign during the Tang Dynasty. [Photo by Chen Xiangzhao / China.org.cn]