In the eight years of Linhai, the anti-animated general Ji Jiguang, with the Taizhou prefecture Tan Lun, transformed the structure of the ancient city wall of Linhai, thickened it, and creatively built 13 two-story hollow enemy platforms, greatly enhancing the defensive ability. used his experience in building a city defense in Linhai to apply to the expansion and enhancement of the Great Wall in the north. The Great Walls of the towns of Cangzhen, Changzhen, Xuanfu, Datong and Shanxi are all improved according to his planning and design. Now Beijing Badaling, Mutianyu, Simatai, Gubeikou, Tianjin Huangyaguan, the old faucet near the Shanhaiguan in Hebei, and the majestic position of the Great Wall, are all left behind by the improvement of Qi Jiguang. It can be said that the ancient city wall of Linhai is called the "teacher" and "blueprint" of the Great Wall of Beijing Badaling.