The hills in the territory belong to the bedrock of the Mount Tai hidden under the Quaternary cover. There is a hill 15 kilometers west of the city, named Ziyang Mountain. It is the only hill in Yanzhou. It is a bare hill of the Ordovician limestone. It is a low hill type. It is divided into two peaks, east peak is 75 meters above sea level, and west peak is 72.5 meters above sea level. The mountain is spread from east to west, 1.5 kilometers long and one kilometer wide, covering an area of 1.5 square kilometers. The rock is limestone, and the Qing Dynasty has been sporadic mining, although it is forbidden. In the later period of the Cultural Revolution, the trees on the mountain were cut down, and the mountain quarry was cut off. The East Peak had become a deep valley, and the west peak still existed.