Introduction to Tongyuan Gate: The predecessor of Tongyuan Gate is Zhenxi Gate. Its base is the Jiangzhou City Wall built by Li Yan, the protector of Shu, in the fourth year of the founding of the Three Kingdoms (AD 226) and the city wall of Jiangzhou built by Peng Peng in the second year of Jiaxi in the Southern Song Dynasty (AD 226). The stone-based structural wall built by Daya to fight against the Mongolian cavalry. The existing city wall and gate ruins are the stone walls built by Dai Ding on the basis of the original city walls in the early Hongwu period of the Ming Dynasty. With the changes of the times and the turbulence of war, the Tongyuanmen City Wall has stood in the wind and rain for more than 600 years, silently witnessing the historical development of Chongqing City.