PANTHEON

One of the world’s greatest buildings, the Pantheon is a perfect structure, still standing with its great dome intact after one thousand nine hundred years. It was a temple to all the gods and has served a variety of functions over its many years. An argument could be made that the Pantheon is the most beautiful, the most perfect building ever constructed. It is one of Rome’s top sites, along with the Vatican, Forum, Colosseum, Piazza Navona and Spanish Steps.

Your first view of the Pantheon will be the huge columns supporting the triangular pediment with splendid dome rising above. It is set in a lovely piazza with a fountain in the center and charming restaurants. Before going in, take time to appreciate the exterior setting. For the best view, stand in the piazza as far back as possible at the beginning of one of the two alleys that lead out from the square. Only here can you appreciate the full effect of the dome rising above the triangular pediment and classical columns of the façade, a most majestic vision. There have been entire books and thousands of articles written about the Pantheon, but here we only present highlights of that much larger story.

This is the oldest Roman building with its original roof still intact. The façade looks somewhat like a Greek temple, similar to the Parthenon built in Athens 600 years earlier, though the Greeks had not invented the dome. Those massive columns in front had a long difficult journey, all the way from Egypt where they were quarried and shaped. Sixteen grey granite columns were dragged on wooden sleds across the desert, floated up the Nile, transferred onto sailing ships for the journey across the Mediterranean, moved to boats that brought them up the Tiber, and then finally hauled about a half a mile to this location. They are monolithic columns, each a single piece of stone 39 feet high and weighing 60 tons, some of the biggest stones ever used. This is most unusual because columns are generally made of many separate pieces in the form of drums stacked atop each other in layers, or made of brick with a marble covering.

Three rows of columns create a portico that holds up a beautiful roof, originally lined with gilded bronze. The barbarians invaded and stripped tons of bronze from Roman buildings in the fifth century, but not this bronze, which lasted here until the time of the Barberini popes in the mid-1600s. The Pope wanted Bernini to use this bronze for the Baldacchino inside St. Peter’s, giving rise to the expression, “what the barbarians couldn’t do the Barberinis did.”

Does the Pantheon look familiar? This monumental combination of columns, triangular pediment and dome has been very influential. The style originated here and has spread all around the world: it is found in the US Capitol building, many state and national capitols, banks, colleges, theaters, hotel lobbies, monuments, mansions, tombs, churches, museums, city halls, libraries, Masonic lodges and more: a thousand copies have sprung up. Some other ancient buildings are larger, such as the Colosseum, bathhouses, and miles of aqueducts, but they are in ruins. Only the Pantheon survives in its entirety.

A marvelous feelingly awaits within, despite all the visitors milling about. There have probably been similar crowds for much of its 2000 year history, and today is no different. Enter through the majestic 40-foot-high bronze doors, the original ones that still open each morning and close to secure the building at night. You may be struck dumb upon entering this amazing space. The dome will capture your spirit, elevated by the vast, heavenly hemisphere that seems to float above you.

You are looking up at the largest dome ever built until the 20th century. The Romans used poured concrete, a construction technique they invented. This is still the world’s largest unreinforced concrete dome, with a diameter measuring 142 feet. Diameter of the dome is equal to its height above the floor -- a hemisphere that would be a complete sphere if extended full circle to the floor. This “sphere” within the Pantheon was intentionally designed to create a symetrically balanced feeling of harmony and balance. The walls are primarily made of brick and covered with a white travertine stone exterior, most of which was stripped away and carted off long ago for other building projects.

The Pantheon wall is 30 feet thick at ground level, while its dome is 21 feet thick at the base. The concrete dome gets gradually thinner as it rises, to just 4 feet thick in the upper portion which is made from lighter materials, a type of volcanic pumice which does not put as much strain at the top of the dome. Another clever building technique which lightened the dome is the large hole at the apex, 30 feet in diameter: it greatly reduces the overall weight while paradoxically strengthening this vulnerable section by acting like a horizontal, round arch or compression ring. Called the Oculus or Eye of God, this hole is the main source of air and light; it never closes, so when it rains, the water comes in and drains out through holes in the floor.

Marble cladding of the walls and floor was added later. There are eight niches all around the interior, shallow barrel vaults which further strengthen the structure and add more space that was probably used for statues of gods. Only one of these niches is not covered in marble and shows the original brick structure of the building. The areas between the niches are like columns or piers, providing a solid foundation for the dome.

Pantheon 10-minute detailed video

Several fascinating optical illusions make the space seem larger than it really is. Ceiling indentations get progressively smaller in each upper row, creating an optical illusion to make the dome seem higher than it is -- things appear smaller as they get further away from the viewer. These square cavities play an important engineering role, reducing the weight of the dome and providing structural strength like I-beams.

This dome is not as big as it seems because the bottom two rows of the coffer squares are not part of a freestanding shell. The standing dome begins above that level and only consists of the upper three rows of coffers and top of the dome. Those two lower levels are part of the wall, which forms the drum holding up the dome, but it was done in such a way as to give you the impression they are part of the freestanding, curved structure. The outside dome is considerably smaller than it appears from the inside because we are led to believe the entire hemisphere is freestanding. Of course, this does not take any credit or praise away from the amazing achievements of the ancient engineers. On the contrary, it shows that they were even cleverer than you might first think.

Legend has it that Emperor Hadrian played a major role in designing the Pantheon; nobody is quite sure. Hadrian reigned from 117 to 138 and was a great military ruler, an astute politician, head of the religion, and a connoisseur of architecture. He was quite the global traveler who liked to survey his kingdom, so during his journeys he was very observant of the different kinds of architecture in foreign cultures. Hadrian’s Villa, 10 miles outside of Rome, had examples of many different kinds of buildings from around his empire. You can still visit it today, although there’s not much left, but combined with a visit to Tivoli gardens, spectacular with their hundreds of fountains, you would have an enjoyable daytrip.

The Pantheon took about eight years to build, constructed on the site of earlier temples which burned down. The previous version of the Pantheon is believed to have been built in the first century BC by Marcus Agrippa, a Roman general, statesman, and son-in-law of Augustus. An inscription written under the triangular pediment outside says “Marcus Agrippa, son of Lucius, Consul for the third time, built this.” It seems that Hadrian preserved the original phrase in a gesture of humility, cleverly sharing the honors with his predecessors.

Originally a temple, the Pantheon is still used for worship as a Catholic church, which is a major reason it survived. In the seventh century it was consecrated as a church, protecting it from demolition or from being mined as a quarry of ready-made building materials (how so many ancient buildings disappeared). This space performed other functions which also helped preserve it: flower market, fish market, mausoleum, and indoor pond where the interior was sometimes flooded so couples could take romantic boatrides. Several prominent figures are buried inside, including Raphael, Annibale Carracci, and two kings of Italy, Vittorio Emanuele II and Umberto I. Anything that keeps a building in constant use is going to safeguard its survival.

Piazza delle Rotonda out front is a lovely space with restaurants ranging from the expensive to McDonald’s. While this is a very touristic location, some of these outdoor eateries are quite popular with local customers, so you might consider having a meal at this ultra-scenic spot, just to enjoy the setting and observe the many people walking by. You might even get lucky with an excellent meal.

There are a few small hotels around the piazza and in the middle is a fountain created in 1575 by Giacomo Della Porta, an important sculptor of the time, with another Egyptian obelisk on top added in 1711, originally carved for the pharaoh Ramses II. Campus Martius, the neighborhood all around, was the heart of ancient Rome extending for several square miles, and densely covered with structures of all types. The Pantheon is the only original building still standing -- everything else we see is from the 16th century and later.

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