 Its Chinese name, "jar walls", refers to the intended strategy whereby attackers coming through the archery tower would be trapped in the barbican, open to attack from all sides.In large gates there may be multiple barbicans – the main gate of Nanjing (Gate of China, Nanjing) had three barbicans, forming the most elaborate system still in existence in China.Towers that protruded from the wall were located at regular intervals along the wall.