Basilica di Santa Maria ad Martyres (The Pantheon)
Here we consider another ancient building, the Pantheon in Rome, which was dedicated in 126 a.d. and has been in continuous use since that time. Between the fourth and seventh centuries, it was owned by the Byzantine emperor, but in 609, Emperor Phocas deeded it to Pope Boniface IV and it became the Basilica di Santa Maria ad Martyres, St. Mary and the Martyrs.
What can account for such longevity? Let us look for clues in its construction, its geometry, the nature of its space, its symbolic significance, and its relatively seamless transition from an imperial and cosmological temple into a place for the Christian liturgy.
Perfect Geometry
From the outside, the Pantheon looks like a conventional Roman temple with a portico where public worship would take place. Traditionally, the cella, the rectangular room behind the porch, would have been private to the priests, containing an altar and perhaps a treasury. Not so in the Pantheon. Invisible from the outside, the interior is instead a vast round room capped with an immense dome.
Domed buildings had come into use in Rome during the first century, but this one is a radical departure. For one thing, the dome is colossal, still the largest unreinforced concrete dome in the world. Only in 1883 did modern construction methods make a larger one possible. Roman engineering was ingenious: as the dome was raised, successively lighter stone was mixed with the cement, from sturdy travertine at the base, to porous tufa above it, and, at the highest level, air-filled pumice stone.
The height of the dome, 190 feet, is the same as its diameter; that is, if it were inverted into the lower space, it would form a perfect sphere, long the symbol of the heavens. Directly beneath the center of the dome is an inlaid marble circle within a square. Just as the dome is half a sphere, so the round room below it is inscribed in a square, which to the ancients symbolized the stasis of the earthly region. Symbolically, this is the perfect geometry of the space where the heavens meet the earth.
Another departure from the norm is the fact that the Pantheon's interior was thrown open to the public. Sacrifices were offered from a central altar, with their smoke exiting through the open dome to the heavens. Oddly, the building faces north, so that entry through the portico is shadowy and dark. A viewer coming through the doors was suddenly thrust into an unexpectedly enormous space, abstract and lacking any relation to the human scale, which dwarfed and awed the unsuspecting entrant. In ancient times, the dome was gilded, and the only light entered through the oculus, the eye of the dome, which is unglazed and open to the sky. Entering the Pantheon was like coming under the golden dome of heaven.
The Cosmos & Its Workings
Even the Pantheon's name was a new departure, and in fact something of a misnomer. It was not really dedicated to all the many gods of the Roman pantheon. The golden dome and the fall of the light through the oculus clue us in to the cosmological significance of the building. The gods honored here were those forces which moved the heavens: the sun, the moon, and the then-known planets—Mercury, Venus, Mars, Jupiter, and Saturn. Statues of these deities stood in the niches which ringed the rotunda.
The light that enters the space from outside might have been understood to symbolize the Platonic concept of the Prime Mover, the immovable and immutable force which by its attraction sets in motion all the elements of the cosmos. The indentations or coffers in the ceiling are seven progressively receding layers deep, as if the hemisphere of the dome were made up of seven overlapping and concentric spheres. Just so were the seven crystal spheres that moved the heavens understood to be. Further, the coffers are arranged in 28 ranks. The number 28 was one of the four perfect numbers known to the ancients: its factors (1, 2, 4, 7, and 14) added together equal 28. To platonic thinkers, number ruled the universe. The Prime Mover was primarily a mathematician.
In addition to being a symbolic rendering of the cosmos, the Pantheon also demonstrated its workings, and functioned as an astronomical calendar and clock. The sweep of the beam of light around the rotunda measured the passage of each day's hours. It marked the weather as well: when the gods rain upon Rome, it rains in the Pantheon. The floor is slightly domed in the middle, to resemble the slight curve of the visible horizon, and to carry rainwater away to the (still functional) drains around the perimeter. On the rare occasion when it snows in Rome, people flock to the Pantheon to watch the magical effect of snowflakes falling through the beam of light.
Light from the oculus also catalogues the symbolic movement of time through the year. At the winter solstice, the darkest time of year, light falls only onto the very top register of the dome, while at the summer solstice the floor is flooded with light. At the equinoxes the light falls onto the base of the dome, marking the midpoints of the heavenly year. But on April 21st, legendarily the date of the founding of Rome, the beam of light passes through a grill set above the main door and into the portico, where on that day the emperor stood, bathed in light, the bridge between the divine order of the cosmos and the earthly empire.
From Pagan Temple to Christian Church
Two emperors are credited with producing this architectural marvel. The first, Trajan, with his chief architect, Apollodorus, probably made the original design and began construction. But Trajan's death put Hadrian on the throne; Hadrian, a brilliant military man and politician, was also a Platonist, an architect, and an astronomer. It is likely he who finished the design and execution. (Apollodorus, who had famously insulted Hadrian's taste for domes, was put to death over an aesthetic disagreement with the emperor.)
The Pantheon survived the centuries relatively unscathed, though repairs were needed in the third century and at some point the dome lost its gold ceiling. Constantine, in a move toward monotheism, was originally a follower of Sol Invictus, the sun god identified with the power of the Prime Mover. So no doubt he would have respected the cosmological reading of the Pantheon. In any case, it remained the possession of the Byzantine emperor until the seventh century, when Emperor Phocas deeded it to Pope Boniface IV.
The Pantheon was the first pagan temple to be converted into a church, and it still possesses a seventh-century icon of the Virgin Mary from the original dedication. The emperor's apse fittingly became the high altar, the earthly ruler deferring to the heavenly King. The lower section has seen many changes, but the impact of the ancient space remains; its dedication to the Virgin Mary seems fitting for what is perhaps the most beautiful building in the world.
Mary Elizabeth Podles is the retired curator of Renaissance and Baroque art at the Walters Art Museum in Baltimore, Maryland. She is the author of A Thousand Words: Reflections on Art and Christianity (St. James Press, 2023). She and her husband Leon, a Touchstone senior editor, have six children and live in Baltimore, Maryland. She is a contributing editor for Touchstone.
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