Philadelphia Skyline

For almost a century no building in Philadelphia rose above the brim of William Penn's hat on City Hall, 548 feet up. There was no law — it was an understanding, honoured by every developer in the city, and it kept Philadelphia's skyline deliberately low while other American cities raced upward.

One Liberty Place broke it in 1987. The city gained a modern skyline almost overnight and, according to local belief, a curse: no Philadelphia team won a championship for the next twenty-four years. When the Comcast Center topped out in 2007 a small William Penn figurine was fixed to the final beam, and the Phillies won the World Series the following season.

Even surpassed, City Hall remains the anchor. It is the largest free-standing masonry building in the world, built without a steel frame, with walls at the base around 22 feet thick to carry the weight. The Penn statue on top is 37 feet tall.

Everything around it is steel and glass from a different century, which makes the composition unusual: the historic building at the centre is not a survivor tucked between towers but the thing they are all arranged around. The model has to get its mass right or the rest of the skyline loses its reference point.

City Hall sits at the centre with William Penn on top, and everything else arranged around it. The Comcast Technology Center is the tallest at 1,121 feet, a plain glass shaft with a lantern at the top; the older Comcast Center beside it is the one with the sloped glass roof.

One and Two Liberty Place are the pair that broke the height agreement in 1987 — stepped, crowned, and deliberately echoing the Chrysler Building. The BNY Mellon Center's pyramidal top closes the western end. The 1901 masonry tower at the middle of all that glass is what makes a Philadelphia model impossible to mistake for anywhere else.