S. Dillon Ripley Views Quadrangle, by Unknown, 1987, Smithsonian Archives - History Div, Smithsonian Secretary S. Dillon Ripley sitting on roof of building across from South Yard. Aerial view of Quadrangle shows Smithsonian Institution Building (SIB) or Castle, Enid A. Haupt Garden, National Museum of African Art (NMAfA) and Arthur M. Sackler Gallery (AMSG). The National Mall and National Museum of Natural History can be seen behind the Castle in the distance..