The Pantheon
Twenty-seven B.C. was an important year for Rome. In January, Octavian proclaimed himself Augustus, becoming the sole ruler of Rome. His son-in-law, Marcus Vipsanius Agrippa, marked the event by laying the foundation for what would become one of Rome’s most famous monuments: the Pantheon.
There is some confusion over what Agrippa’s original Pantheon looked like, what it was for, and even whether it was called the Pantheon at all. The second-century historian Dio Cassius wrote that Agrippa had intended to erect a great statue of Augustus inside and dedicate the temple to the new emperor, but Augustus wisely refused the honor: Julius Caesar, his adoptive father, had been assassinated due to fears that he had kingly ambitions.
Dio Cassius speculated that the temple may have been dedicated to the gods of Rome, or – his own preferred theory – “that its dome resembled the heavens.” His writings have caused headaches for historians – not only because dedicating a temple to all the gods was unusual, but also because the reference to a dome makes it unclear if he is writing about Agrippa’s original structure or a later incarnation.
Whatever its form or function, Agrippa’s Pantheon was badly damaged by fire in A.D. 80 and repaired by Emperor Domitian. Later, as part of an urban reform effort begun by Emperor Hadrian shortly after his accession in 117, the old temple was pulled down to make way for the building that stands today.
When the Pantheon was rebuilt during Hadrian’s rule, it broke new architectural ground, but the exterior might have deceived visitors into thinking the new temple was traditional. From the outside, the Pantheon still resembled a traditional Greco-Roman temple, with a triangular gable borne on 16 Corinthian columns. The traditional facade was impressive, but no one could ever have anticipated the magnificent sight awaiting them inside.
Upon entering, the initial impression was of a vast, soaring space. Today, just as 2,000 years ago, the architecture draws the gaze upward to the curving surface of the dome. At about 142 feet in diameter, it was, for centuries, the widest unsupported span ever built. There is some debate as to whether the 15th-century dome over Florence’s Santa Maria del Fiore equals or surpasses the diameter of the Pantheon’s dome. In any case, both structures were only bested by modern construction techniques in the 20th century.
The lower levels of the dome were made using concrete combined with fragments of porous limestone. As the dome rises, the concrete contains lighter stone. At the very top of the dome is a round window, called the oculus, where sunlight streams in. Measuring about 27 feet across, this opening is the Pantheon’s only light source.
How Roman architects solved the technical problems involved in the construction of such a large dome has long confounded scholars. Beyond the enigma surrounding its construction, there is also much debate over the Pantheon’s symbolism. Dio Cassius’ speculation that the building’s ceiling symbolizes the “celestial dome” has endured since the second century. In his view, the earthly realm corresponds to the ground levels of the building, while the heavens were embodied by the magnificent curves of the cupola.
Then, as now, the light filtering through the oculus progressively moves around and illuminates the niches of the rotunda depending on the time and the season. At noon on April 21, the date of Rome’s founding, the sun’s rays directly fall on the entrance to the rotunda. Upon entry to the temple, a figure – perhaps it was once Hadrian himself? – would be bathed in sunlight, a moment of symbolic significance that would place him at the center of the empire. Even if the Pantheon was never intended as a literal re-creation of the cosmos, the carefully designed proportions of the building do seem to suggest parallels between the workings of the heavens and earthly imperial power.
LUIS BAENA DEL ALCÁZAR,
NATIONAL GEOGRAPHIC HISTORY