Complex sentence: The Union later functioned as a general dining hall for students, and was its interior was mostly demolished when Harvard University, having obtained the building and turned it into the Barker Center for Humanities in the late 20th Century.
Split into simpler sentences: The Union later functioned as a general dining hall for students. Its interior was mostly demolished when Harvard University, having obtained the building and turned it into the Barker Center for Humanities in the late 20th Century.