 The outer rampart comprises a perimeter of 8 km and is lined with guard towers.The ramparts still stand up to 12 m high and are 25 m in width at their base.Besides, part of the inner rampart was cut through for the purpose of archaeological investigation, which was dated from 400-350 BC.And it was suggested that this rampart was constructed by a local and indigenous society prior to the colonization of Han dynasty.