Located at the northeast cornor of Beihai, Xian Can Altar covers an area of 17,000㎡. It was originally the former site of Leiting Hongying Hall in the Ming Dynasty. In the 7th year of the Qianlong period of the Qing Dynasty, the Altar was built, serving as the place where concubines worshiped Silkworm Goddess. There are Silkworm Viewing Platform, Hall of Silkworm, Back Hall, Silkworm Workshop, Well Pavilion, Livestock Pavilion, Corridor, Mulberry Garden and so on. To the east, there is a small river running north and south called "Bathing Silkworm River", a water system introduced to the east of Beihai by the Jinshui River in the Yuan Dynasty. The Xian Can Altar is one of the nine altars in Beijing, and is a relatively complete surviving place where the imperial court worshiped silkworm goddess.