Introduction to the Great Wall Tunnel of the Ming Dynasty: The Great Wall Tunnel of the Ming Dynasty was built in the 13th year of Hongwu in the Ming Dynasty. When the famous general Xu Da was building the Jiumenmen section of the Great Wall, he designed and dug a tunnel from the inside of the Great Wall based on the dangerous geographical location of the Jiumenmen section. The school military field secretly leads directly to the secret passage in the mountains outside the customs. The tunnel is located in the mountain below the Great Wall, with a total length of 1,027 meters, and a total of two exits and one entrance. The tunnel is equipped with toilets (latrines), confinement rooms, military rooms, water prisons, grain storage rooms, kitchens, well rooms and other caves, which can accommodate about 2,000 people.