The Pantheon: The Mysteries and Secrets of the World's Largest Dome

Rome's Pantheon has stood for nearly 2,000 years, surviving barbarian attacks, medieval despoiling, and papal plunder that left almost nothing else of ancient Rome intact. Why was the Pantheon spared?

You’ll learn the answer to this and many other fascinating mysteries on this self-guided tour.

The tour begins right in front of the Pantheon, in Piazza della Rotonda, where you'll learn some of the rules of classical architecture that make its facade so visually arresting. You’ll also decode the monument’s inscription, and find out why it gives credit to a man who lived 200 years before it was built. Once inside, you'll uncover the engineering feats behind the dome's near-miraculous survival as well as the ancient secret that makes it the largest unsupported dome in masonry in the world—even to this day.

You’ll discover how a temple built to house Rome's twelve gods became a Christian church, a royal mausoleum, and the architectural blueprint for some of the world's most celebrated domes. You'll hear about the Renaissance architect who literally climbed inside the Pantheon's walls to unlock dome-building technology that had been lost for 13 centuries—and built one of Italy’s most famous churches with the knowledge he gained.

The tour ends just outside, near the Tazza d'Oro coffee bar, where a quirk in the facade reveals an architectural mistake hiding in plain sight for nearly 2,000 years.

On this 60-minute tour, you'll have a chance to:

• Uncover the secrets of Roman concrete and how it actually strengthens over time, unlike modern cement
• Learn how the oculus functions as a sundial, with a beam of light illuminating the entrance doors on Rome's legendary founding date
• See the tomb of the great Raphael, and hear the story of his tragic death on his 37th birthday
• Find out why Michelangelo refused to build the dome of St. Peter's Basilica bigger than that of the Pantheon
• Discover how the present building is not the first—or even the second—Pantheon to stand on this spot
• Locate the the holes cut into the Pantheon’s inner walls by the father of Renaissance architecture, Filippo Brunelleschi
• Marvel at the masterful ancient engineering that makes the massive bronze doors so easy to open and close

The Pantheon rewards anyone willing to look closely, and this tour gives you the knowledge to see what most visitors walk right past.