Introduction to the main hall: A plaque hangs high in the center of the main hall, with the words "Houtang" written on it, which is derived from Fan Zhongyan's famous saying "Be anxious when the world is worried, and be happy after the world is happy." The two pillar-holding couplets on both sides "Believe deeply in heaven and love others deeply, enrich the country and benefit the people, and establish a virtuous example; study deeply in natural history, practice agricultural politics, and combine Chinese and Western knowledge to create great achievements." was written by the famous calligrapher Qi Shuyu on the 350th anniversary of Xu Guangqi's death.