Designed by John McArthur, Jr. in the Second Empire style, and influenced by the Tuileries Palace and the Louvre, Philadelphia City Hall is one of the world's largest all-masonry, load-bearing structures without a steel frame. Construction began in 1871 and wasn't completed until 1901. City Hall is a square doughnut of a building that occupies a 4-block site at the center of the downtown. In the middle of each side is an arched portal leading into the central courtyard, and its north side includes a 548 ft clock tower. Until 1987, this tower was the tallest structure in the city.