Tuancheng, located next to the main entrance of the Beihai Sea, is a small round castle. The castle wall is not high, small and chic, it feels more fun than defense functions, after all, it used to be in the imperial city, safe. Through the city gate, follow the curved ladder of the city wall, and you will reach the Tuancheng. The upper is flat, the middle is the main hall of the Chengguang Temple, inside is the Burmese Jade Buddha. Outside the temple is a large jade bowl that is said to be the wine of the Yuan Dynasty Kublai. There are also several ancient trees in the city, and one big tree is said to be the shade of the Qianlong emperor's imperial seal. Standing on the wall of Tuancheng, you can see the white tower of Qionghua Island in Beihai from the north, looking south to see the Zhongnanhai Lake, and looking west to the Beihai Bridge. Tuancheng is not many tourists every day, it is quite quiet, the ticket is only 1 yuan, it feels like the price in the 1980s, it is worth buying a ticket to take a look.