It is the Main Building. Its west, east, and middle parts are connected by four arcades. With a total floor area of over 76,000 m2, the huge building was second to none among all colleges in the 1960s. It was designed by hundreds of teachers and students from various departments as part of their graduation projects. It has seen the past days of vicissitudes, glory, dreams of Tsinghua teachers and students. It will also embrace another century of achievements.