What is the Pantheon?

An astounding triumph of the Roman Empire, the Pantheon pays tribute to ingenuous engineering, devout worship, and innovative culture. Once erected, the giant domed temple in Rome, Italy, forever changed the way the world thinks of architecture. Through fire and desecration, rechristenings and rededications, the Pantheon remains a classical example of human achievement.

Unfortunately, the Pantheon we can visit today is not the original incarnation. The first temple, not named Pantheon, was build by Marcus Agrippa in 27 BCE, but tragically burned down in 80 CE. Domitian made a second attempt a few years later. In 110 CE he too was thwarted by fire. Finally, Emperor Hadrian restored and rebuilt the worship site as the Pantheon, "Temple of All of the Gods."

Elements in the design and construction of the Pantheon speak to several new ideas of the Roman architects. First of all, although the dome is the central feature, it is obscured at eye level from the exterior of the temple by a more traditional portico. The columned and rectangular entryway gives a plain, understated facade to the breathtaking interior. It is unusual in such ancient buildings to favor the interior over the exterior in this manner.

Secondly, as the first semispherical dome built in the world, it was a feat in construction. Romans were skilled with concrete and mathematics. They knew how to use light rock, like pumice, in the aggregate concrete of the ceiling, yet heavy rock like basalt in the foundation. Instead of columns and cross braces, they exploited the inherent stability of arches to support the giant dome. The Pantheon has a spectacular interior height of 143 ft (43 m), which is equaled by the diameter of the chamber. This perfect proportion was in keeping with their reverence for the holiness of circles.

Constantine and his Christianizing of Rome led to major changes at the Pantheon. There used to be rows and rows of bronze roses adorning the ceiling, in panels called coffers. These glowing ornaments matched the two giant bronze doors that led into the dome. The Renaissance ruler, Barberini, stole all the bronze roses in the temple to melt down and use in the Catholic St. Peter's Cathedral. The Pantheon was the first pagan temple to become a Catholic church in 609 CE, when its name was changed to Santa Maria ad Martyres, as it remains today.