Architects: Harrison and Abramovitz The Alcoa Building is the most prominent of the new structures that face onto Mellon Square. It is a thirty-story skyscraper that was designed as a showpiece of the use of aluminum in building construction. Aluminum was used wherever possible, from the skin of the building to its utilities, reducing the weight of the building so those substantial savings could be made in the structure's steel frame. The Alcoa Building stands on the site of the renowned Beaux Arts-style Nixon Theater. Harrison and Abramovitz was one of the most famous architecture firms in the U.S. at mid-century and was responsible for many buildings in Pittsburgh (including the USX Tower and Four Gateway Center).