The Influencial Architecture of the Pantheon in Rome

Details of the Pantheon, Rome
Details of the Pantheon, Rome. Photo by Victor Spinelli/Getty Images
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Introduction

Piazza della Rotonda with 18th century fountain, Fontana del Pantheon, and the Pantheon
Piazza della Rotonda with 18th century fountain, Fontana del Pantheon, and the Pantheon. Photo by J.Castro/Moment Mobile Collection/Getty Images

It's not the Pantheon's facade facing the Italian piazza that makes this architecture iconic. It is the early experimentation with dome construction that has made Rome's Pantheon important in architectural history. The portico and dome combination has influenced Western architectural design for centuries.

You may already know this building. From Roman Holiday in 1953 to Angels and Demons in 2009, films have featured the Pantheon as a ready-made movie set. The Pantheon in Rome has become a destination not only for tourists and filmmakers, but also for architects, designers, and artists from around the world. Its geometry has been measured and its building methods have been studied, as explained in this article.

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Parts of the Parthenon

Pictorial Diagram Illustrates Interior and Exterior of the Pantheon in Rome
Pictorial Diagram Illustrates Interior and Exterior of the Pantheon in Rome. Illustration by De Agostini Picture Library/Getty Images (cropped)

The Pantheon portico or entryway is a symmetrical, classical design with three rows of Corinthian columns—8 in the front and two rows of 4—topped by a triangular pediment. The granite and marble columns were imported from Egypt, a land that was part of the Roman Empire.

 But it is the Pantheon's dome—complete with an open hole at the top, called an oculus—that has made this building the important architecture it is today. The geometry of the dome and the oculus sunlight moving throughout the interior walls have inspired authors, filmmakers, and architects. It was this domed ceiling most of all that influenced a young Thomas Jefferson, who brought the architectural idea to the new country of America.

Pantheon or Parthenon?

The Pantheon in Rome, Italy should not be confused with the Parthenon in Athens, Greece. Although both were originally temples to gods, the Greek Parthenon temple, atop the Acropolis, was built hundreds of years before the Roman Pantheon temple.

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History of the Pantheon in Rome

Pediment of the Pantheon, Rome, Italy
Pediment of the Pantheon, Rome, Italy. Photo by Cultura RM/Franck Sauvaire/Collection Mix: Subjects/Getty Images (crop)

The Pantheon in Rome was not built in a day. Twice destroyed and twice rebuilt, Rome's famous "Temple of All the Gods" began as a rectangular structure. Over the course of a century, this original Pantheon evolved into a domed building, so famous that it has been inspiring architects since before the Middle Ages.

Archaeologists and historians debate which emperor and which architects designed the Pantheon we see today. In 27 B.C, Marcus Agrippa, the first emperor of the Roman Empire, commissioned a rectangular Pantheon building. Agrippa's Pantheon burned down in 80 A.D. All that remains is the front portico, with this inscription:

M. AGRIPPA L. F. COS. TERTIUM FECIT

In Latin, fecit means "he made," so Marcus Agrippa is forever associated with the Parthenon's design and construction. Titus Flavius Domitianus, (or, simply Domitian) became Rome's Emperor and rebuilt Agrippa's work, but it, too burned down in about 110 A.D.

Then, in 126 A.D., Roman Emperor Hadrian completely rebuilt the Pantheon into the Roman architectural icon we know today.  Having survived many centuries of wars, the Pantheon remains the best-preserved building in Rome.

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From Temple to Church

Floor plan of the Pantheon as an Ancient Roman Temple
Floor plan of the Pantheon as an Ancient Roman Temple. Photo by Kean Collection/Archive Photos Collection/Getty Images

The Roman Pantheon was originally built as a temple for all the gods. Pan is Greek for "all" or "every" and theos is Greek for "god" (e.g., theology). Pantheism is a doctrine or religion that worships all gods.

After the 313 A.D. Edict of Milan established religious tolerance throughout the Roman Empire, the city of Rome became the center of the Christian world. By the 7th century, the Pantheon had become St. Mary of the Martyrs, a Christian church.

A row of niches lines the rear walls of the Pantheon portico and around the perimeter of the dome room. These niches may have held sculptures of pagan gods, Roman emperors, or Christian saints.

The Parthenon was never early Christian architecture, yet the structure was in the hands of the reigning Christian Pope. Pope Urban VIII (1623-1644) pilfered precious metals from the structure, and in return added two bell towers, which can be seen on some photos and engravings before they were removed.

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Bird's Eye View

Aerial View of the Pantheon in Rome, Dominated by the Dome and Oculus
Aerial View of the Pantheon in Rome, Dominated by the Dome and Oculus. Photo by Patrick Durand/Sygma via Getty Images (cropped)

From above, the Pantheon's 19-foot oculus, the hole at the top of the dome, is an obvious opening to the elements. It allows sunlight into the temple room below it, but also allows rain to the interior, which is why the marble floor below curves outward to drain the water.

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The Concrete Dome

Pantheon Dome and Relieving Arches
Pantheon Dome and Relieving Arches. Photo by Mats Silvan/Moment Open/Getty Images (cropped)

The ancient Romans were skilled at concrete construction. When they built the Pantheon around 125 A.D. the skilled builders of Rome applied advanced engineering to the Greek classical orders. They gave their Pantheon massive 25-foot thick walls to support a huge dome made of solid concrete. As the height of the dome rises, the concrete was mixed with lighter and lighter stone material—the top is largely pumice. With a diameter that measures 43.4 meters, the dome of the Roman Pantheon ranks as the world's largest dome made of unreinforced solid concrete.

The "step-rings" can be seen on the outside of the dome. Professional engineers like David Moore have suggested that the Romans used corbeling techniques to construct the dome—like a series of smaller and smaller washers set upon each other. "This work took a long time," Moore has written. "The cementing materials properly cured and gained strength to support the next upper ring....Each ring was built like a low Roman wall....The compression ring (oculus) at the center of the dome...is made of 3 horizontal rings of tile, set upright, one above the other....This ring is effective in properly distributing the compression forces at this point."

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The Amazing Dome at the Roman Pantheon

Inside the Pantheon in Rome, Italy.
Sunlight shining through an oculus illuminates the interior of the Pantheon in Rome, Italy. Photo by Mats Silvan/Moment Open/Getty Images

The ceiling of the Pantheon dome has five symmetrical rows of 28 coffers (sunken panels) and a round oculus (opening) at the center. Sunlight streaming through the oculus illuminates the Pantheon rotunda. The coffered ceiling and oculus were not only decorative, but lessened the weight load of the roof.

 

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Relieving Arches

Relieving Arches on the Curving Wall of the Pantheon Dome in Rome
Relieving Arches on the Curving Wall of the Pantheon Dome in Rome. Photo by Vanni Archive/Getty Images (cropped)

Although the dome is made of concrete, the walls are brick and concrete. To support the weight of the upper walls and dome, brick arches were built and can still be seen on the exterior walls. They are called "relieving arches" or "discharging arches."

"A relieving arch is usually of rough construction placed in a wall, above an arch or any opening, to relieve it of much of the superincumbent weight; also called a discharging arch."—Penguin Dictionary of Architecture

These arches provided strength and support when niches were carved out of the interior walls.

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Architecture Inspired by Rome's Pantheon

Dome at Massachusetts Institute of Technology
Dome at Massachusetts Institute of Technology. Photo by Joseph Sohm/Getty Images (cropped)

The Roman Pantheon with its classical portico and domed roof became a model that influenced Western architecture for 2,000 years. Andrea Palladio (1508-1580) was one of the first architects to adapt the ancient design that we now call Classical. Palladio's 16th century Villa Almerico-Capra near Vicenza, Italy is considered Neoclassical, because its elements—dome, columns, pediments—are taken from Greek and Roman architecture.

Why should you know about the Pantheon in Rome? This one building from the 2nd century continues to influence the built environment and the architecture we use even today. Famous buildings modeled after the Pantheon in Rome include the U.S. Capitol, the Jefferson Memorial, and the National Gallery in Washington, D.C.

Thomas Jefferson was a promoter of the Pantheon's architecture, incorporating it into his Charlottesville, Virginia home at Monticello, the Rotunda at the University of Virginia, and the Virginia State Capitol in Richmond. The architectural firm of McKim, Mead, and White were well-known for their neoclassical buildings throughout the U.S. Their Rotunda-inspired domed library at Columbia University—the Low Memorial Library built in 1895—inspired another architect to build the Great Dome at MIT in 1916.

The 1937 Manchester Central Library in England is another good example of this neo-classical architecture being used as a library. In Paris, France, the 18th century Panthéon was originally a church, but today is best known as the final resting place for many famous Frenchmen—Voltaire, Rousseau, Braille, and the Curies, to name a few. The dome-and-portico design first seen in the Pantheon can be found throughout the world, and it all began in Rome.

Sources: The Penguin Dictionary of Architecture, Third Edition, by John Fleming, Hugh Honour, and Nikolaus Pevsner, Penguin, 1980, p. 17; The Pantheon by David Moore, P.E., 1995, romanconcrete.com [accessed July 28, 2017]