"D" is for Dome

It's a thrill to stand beneath the round coffered ceiling of the Pantheon in Rome. I gazed up at the sky through the open central skylight as others have done for 2,000 years. (For the inevitable rainy days there are drainage holes in the floor beneath the opening.) And until the Renaissance the Pantheon had the largest dome in the world. 

The Pantheon, Rome

Central Skylight, or Oculus, in the Pantheon Dome

This dome was so amazing that Renaissance architect Filippo Brunelleschi came to Rome centuries later and got permission to cut into the Pantheon's dome to study its structure. The spot where Brunelleschi cut can still be seen.

Brunelleschi's Cut in the Pantheon Dome

He returned to the city of Florence where the cathedral had a gap in its ceiling – no one at the time knew how to bridge such an large expanse. Inspired by what he'd learned at the Pantheon, Brunelleschi covered the opening. Santa Maria del Fiore with its distinctive red dome is now known as Il Duomo.

Santa Maria del Fiori, Florence

The Pantheon also inspired another great Renaissance dome, that of St. Peter's Basilica in Vatican City. This was Michelangelo's last project and is now the largest dome in the world.

The Dome of St. Peter's Basilica, Vatican City

Interior of Michelangelo's Dome

The creative inspiration that began at the Pantheon in Rome continued on to influence more domes at St. Paul's Cathedral in London and the United States Capitol in Washington, D.C. – not bad for an idea 2,000 years old.

Next:  "E" is for Eruption