Introduction to Wailuo City: Xianling Mausoleum has high walls built around the mausoleum area, which are opposite to the walls of the mausoleum area, and are called Wailuo City and Neiluo City respectively. The addition of the Xianling Mausoleum was modeled on the Seven Tombs of Tianshou Mountain. However, these Seven Tombs only have walls surrounding the mausoleum area. Each mausoleum does not have a separate Wailuo City. There is only a heavily defended city wall built around the Tianshou Mountain Mausoleum area. After the Xianling Mausoleum, when Sejong built the Yongling Mausoleum for himself, he added a Wailuo City outside the wall of the mausoleum area, which was imitated by later Dingling Mausoleums, forming a unique imperial mausoleum system.