Introduction to the inner city: After crossing the Royal Bridge for 40 meters, you will enter the inner city. Before the restoration, there are still ruins of the original site. There are three doors on the south wall, called the mausoleum gate. The middle door is about 3.6 meters wide, and the left and right doorways are about 3.2 meters wide. The middle door is single-tall, and the side doors are shorter. The wings are juxtaposed, and it is a door-hole type bracket building. There is a wall around it that is 3.7 meters high, 0.7 meters wide, and 1.4 meters thick. It is an ice plate eaves type masonry structure. The walls are made of 40 cm long blue bricks, which are extremely strong. In the early years, turrets were built at the four corners of the inner city wall for the mausoleum guards to protect. The layout is rigorous and each has its own pattern. There is a partition wall in the middle of the inner city, and the courtyard is divided into front and rear. The front yard is slightly larger than the back yard, and it is higher in the back and lower in the front.