The Largest Dome in the World

As any visitor to Rome can tell you, this city is filled with lots and lots of domes. Which one is the largest?

peters domeMost people will instinctively tell you that it’s the dome of St. Peter’s Basilica–and in one sense they’re right. Standing 136.57 m (448.1 ft) high, it is the tallest dome not only in Rome, but in the entire world.

But there’s another dome in Rome which actually has a larger diameter than that of St. Peter’s. The dome of the Pantheon is 43 meters (142 ft) in diameter–one meter wider than St. Peter’s dome. (Bet you didn’t know that.)

pantheon domeThis wasn’t an accident, either. On the contrary, making St. Peter’s dome a bit less wide than the Pantheon’s was a deliberate decision, made by Michelangelo himself.

The great Michelangelo wasn’t the original director of the building project that eventually erected St. Peter’s Basilica, and in fact his own proposed design was rejected! Sangallo submitted a proposal for a much more complex and bigger basilica, dome sangallowhich originally caught Pope Julius II’s fancy. We’re probably lucky that it was never realized, however; many architects at the time were convinced that it was structurally unsound, and would have collapsed…

To make a very long story short, several different artist/architects were in charge of building St. Peter’s, but over the decades, every time that one of them died and another took his place, the basilica’s design-plan got changed. By the time construction-workers got around to building the dome, an elderly Michelangelo had taken the helm, and he altered the design yet again.

Piazza della Rotonda, Pantheon, RomeIn deference to the unknown (but probably Greek) ancient architect who designed the Pantheon, Michelangelo decided to make the dome of St. Peter’s one meter smaller in diameter. It would certainly have been possible to make it a little wider; but this was Michelangelo’s tribute to ancient Greece and Rome.

That’s why to this day, the dome of the Pantheon is still the widest dome in Rome. It’s not very tall, to be sure, and so on the skyline of the city it is easily missed … but it continues to hold top-rank in this one sense, to this very day.