Tuancheng is located on the west side of the South Gate of Beihai. In the Yuan Dynasty, it was a small island. In the Ming Dynasty, it was rebuilt and the city wall was built. The water surface in the southeast was filled with flat land, basically forming the scale and surrounding environment. In the 19th year of Emperor Kangxi of the Qing Dynasty (1680), the Chengguang Hall was rebuilt and the original semicircular hall was transformed into a cross-shaped plane. During the reign of Qianlong, major construction was carried out, and the Jade Urn Pavilion was added. Tuancheng today is basically a complex of buildings built during the Qianlong period. Its plane is round, and the city is built with thousands of brick walls. The city platform is 4.6 meters above the ground, with a circumference of 276 meters and an area of 4,553 square meters. There is a gate along the wall on the east and west sides of the city wall. The gate tower is built on the upper side. The east is Zhaojing and the west is Yanxiang. The entrance can be climbed along the road to the top of the city. Cover doors are set at each stepping road, and the layout of the buildings on the city platform adopts a symmetrical layout with gardens. Chengguang Hall is the center of the city platform, with the Jade Weng Pavilion in the south and Jingji Hall in the north, forming the central axis of the city platform. Arranged symmetrically on both sides, there are Gulaitang, Yuqingzhai Dongyu and Xiyu. Duoyun Pavilion and Jinglan Pavilion are high on the rockery. The whole city has yellow tiles and red walls. There are dozens of green pines and cypresses planted in the splendid ancient buildings. The center of Chengguang Hall is square, with three rooms wide and three deep, and one embossing room on each side. The entire plane is cross-shaped. There is a platform to the south. The central hall is a double-eave Xieshan top, and the embossed mansion is a single-eave Xieshan roll shed, covered with yellow glazed tiles and green trim tiles, with flying eaves and corners. The upper eaves are heavy with seven buckets, and the lower eaves and hugs are heavy with five buckets. In the hall, there is a color painting of a large gold spinner. The jade urn in the jade urn pavilion is a work of the Yuan Dynasty, large in size and exquisitely carved.