Introduction to Congshu Building: Congshu Building is a separate courtyard of Geyuan, located opposite Geyuan. It was originally the former site of Xiaolinglong Mountain Hall owned by brothers Ma Riwan and Ma Rilu, another major salt merchant in Yangzhou. The collection of books in the Xiaolinglong Mountain Library is known as "the largest collection of books in the north and south of the Yangtze River". Emperor Qianlong also received them when he went to the south of the Yangtze River. "Er Ma" is generous and hospitable. Scholars from all over the world can come to his home to read and study, and some even stay at his home.