At the end of each of the AIB’s four halls are tall, tapering towers, designating the four primary entrances of the building. The halls were designed to provide both shelter for the ground floor entrance doors and support space on the upper floors. The towers remain structurally intact, but are used primarily for administrative use by Smithsonian Institution staff.
Together with the towers, the pavilions act as buttresses for the open arcades between the AIB’s Rotunda, halls, courts, and ranges. The pavilions are the corner posts, both literally and figuratively, for the building. As with the towers, the pavilions are used mainly as office and laboratory space for museum employees. Of all the pavilions, the North West Pavilion, which housed the offices of the Director and had more detailed finishes, is considered the most significant.