Introduction to Xuanruitang: Xuanruitang is located in the middle of the entire building, facing south. To the north is the Fenglai Hall and the North Gate across the patio, to the south is the West Pool, and the east and west sides are connected by verandas. The name "Xuanruitang" of the former Jiangning Weaving House was given by the emperor in the 38th year of Kangxi (1699 AD). It is said that Cao Yin's mother Sun (Cao Xueqin's great-grandmother) was Emperor Kangxi's wet nurse when he was a child, and Cao Yin served as an imperial guard when he was young. To Emperor Kangxi, Mrs. Sun could be described as a kind and loving mother. Emperor Kangxi's inscription obviously contains a sense of gratitude to the wet nurse. Xuan Ruitang also witnessed the extraordinary relationship between the Cao family and Emperor Kangxi.