Photo taken on June 15, 2017 shows horse bones at the Zheng State tomb at Xinzheng City, central China's Henan Province. The excavation of a Zheng State tomb from the Spring and Autumn Period (770 B.C. - 476 B.C.) has already found more than 20 chariots and a large amount of horse bones. (Xinhua/Zhu Xiang)