Carnegie Science Hall is named for its major benefactor, Andrew Carnegie. The vast building houses the classrooms and laboratories of the biology, geology, and physics and astronomy departments. A major addition and renovation in 1990 nearly doubled the building's size; among the additions were new laboratories, lecture and seminar classrooms, common spaces for interaction among faculty and students, and the Ladd Planetarium. A rooftop greenhouse and 0.5-meter observatory are among the building's more notable features.