The Calpine Center is a 453 ft (138m) tall postmodern skyscraper in Downtown Houston, Texas. The building has 33 floors of Class A office space. The building has the world headquarters of Calpine Corporation. Hines and Prime Asset Management jointly developed the building. The Houston office of HOK designed the building, and Turner Construction acted as the general contractor. It is connected to the downtown tunnel system. Mark Russell of Studley, a real estate firm, said that the Calpine Center is more efficient than many of the tall office buildings built in Houston in the early 1980s.