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. It is the 30th tallest building in the city. 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.