Introduction to the defense system: The "Gaotai Pingshan Castle" (total altitude 92 meters) consists of Jishan Mountain (45.6 meters) and surrounding flat land. There is a trench city built around it, and stone walls and walls guard the castle. At the same time, each city area or each passage is separated by stone walls and walls, making it impossible for foreign enemies to easily enter. The stone wall is steeply sloping. This feature is called a "fan-shaped slope", and the upper part tilts outward, making it difficult to climb. Gray tiles and white walls, all exterior walls are coated with white mortar for fire protection.