At 50 stories, this Greek-influenced glass skyscraper is one of Chicago's Postmodern masterpieces. It is arguably the most prominent high-rise in Chicago not designed by an American architect; its Spanish architect also designed Citadel Center a decade later. The building was originally the world headquarters of R.R. Donnelly and later United Airlines. Its most striking exterior feature is a triangular pediment crown, a nod to neo-classical architecture such as the Art Institute. The unusual, geometric piers and spandrels are clad in Portuguese granite. The classical Greek connection is emphasized throughout the meticulously-designed lobby with generous use of Thassos marble, one-of-a-kind art installations and a reflecting pool.