Introduction to Ci Shu Building: The first floor of the fifth floor of the Chen family is the "Ci Shu Building". The original name of Ci Shu Building is Ci Shu Pavilion. It is the place where Chen Ruolin collects the books given by Emperor Daoguang. It was built in the fourth year of Daoguang ( 1824), with a plaque inscribed by calligrapher Weng Fanggang. In the third year of Xuantong (1911), Chen Ruolin's great-grandson Chen Baochen taught the emperor in Yuqing Palace and gave him a horse in the Forbidden City. The emperor gave Chen Baochen more books from the imperial collection. In order to repay the emperor's favor, Chen Baochen built a new building behind the Chengcuo at the back gate. The books and plaques in Cishu Pavilion were moved here and renamed "Ci Shulou".