Philadelphia City Hall Clock
Philadelphia's City Hall is almost 550 feet tall, if you count the 37-foot statue of William Penn that stands on the top of its spire. Built with marble, limestone and granite, it is one of the tallest remaining masonry buildings in the world. The clock itself has four faces, each of which measures 26 feet in diameter. Visitors can climb to an observation area above the clock, at the foot of the William Penn statue.