The tallest building in Pennsylvania is the 60-story Comcast Technology Center in Center City Philadelphia, which is 1,121 feet (342 m) in height. The mansion or the Big House is example of Greek Revival architecture in the United States and is a National Historical Landmark.The tallest tower in the world when built due to an incredible feat of masonry, it's walls are up to 22ft (6.7m) thick and made of granite and brick. Constructed in the late 1800s, Philadelphia's City Hall is perhaps the largest and most elaborate seat of municipal government in the nation. From the Philadelphia Museum of Art to Independence Hall, these buildings are the heart and soul of this city.