The Sears Tower—Harvard Observatory is a historic astronomical observatory that is part of Harvard Observatory and is located at 60 Garden Street in Cambridge, Massachusetts. Now just a portion of the observatory's Building A, the Sears Tower is the oldest portion of the complex, designed by Isaiah Rogers and constructed in 1843. This structure is a square brick building, with a projecting cornice and a Greek Revival entrance framed by pilasters. The dome was equipped with a 15-inch telescope, the state of the art at the time.