City Hall is truly unique and famous for its gothic architecture and statues built into its design. Construction begun in 1871 and took over 30 years to complete. The first floor is built of solid granite, 22 feet thick in some places, supporting a brick structure faced with marble. The 548-foot tower is the tallest masonry structure in the world without a steel frame. It was the tallest building in Philadelphia until 1986, ending an informal gentlemen's agreement that had limited the height of buildings in the city to no higher than the statue of William Penn that sits atop the building.