Introduction to the Zhenwu Hall: The Zhenwu Hall of the ancient castle was rebuilt in the 13th year of Jiaqing in the Qing Dynasty. It is located above the North Fort Gate and is the lock of the entire castle. In the hall, there are horned dragons circling around each other, blue birds flying in the sky, painted pillars and carved beams, which are gorgeous and spectacular. It is accompanied by the Peach Blossom Girl, Duke Zhou and the turtle and snake generals. The back wall is painted with twelve birds playing pictures, and the two sides are painted with the story of Emperor Xuan's cultivation. The skills are delicate and the pen is vivid. The glazed ridged beasts, figures playing with heads and wings, and the brick and stone carvings in the main hall are unique and exquisitely crafted and are the essence of the castle's architecture. Because the Zhenwu Hall is located at the top of the castle, looking down, you can have a panoramic view of the entire castle. In particular, the ancient street along the central axis of the castle has an "S" shape, and there are two half-moon-shaped waterlogging ponds next to it, forming a yin and yang shape. The streets and alleys have mottled stone foundations, and the ancient houses are dotted with green shades. Outside the fort is the majestic and green Mianshan Mountain. Looking around, it can be said that "the scene is in the hexagram and the people are in the painting."