The dome of the Pantheon is the largest unreinforced concrete dome in the world, an extraordinary achievement for a building constructed in 26AD (or indeed at any point in history).
About the Pantheon
Undoubtedly one of the most famous buildings in Rome, the Pantheon is found nestled in amongst the surrounding buildings at the very heart of historic Rome. I visited in the morning just half an hour or so after the building opened, and in the mid-afternoon – it is definitely worth going early to get a real sense of the space within before the crowds arrive. The rotunda, or dome, is one of the most extraordinary things I have ever seen.
Built in 126AD by the Roman Emperor Hadrian, the Pantheon is one of the best preserved buildings of Ancient Rome having survived the transition from temple of the Roman gods to Catholic church – a transition that few Roman temples made, most being left to ruin. Within the shell of the building itself, the interior has been subjected to a number of changes over the years, most notably in the 17th century when the bronze ceiling of the portico was removed and made in to cannons for the Castel Sant’Angelo. The marble interior is largely original, but with extensive restoration however.
There is a beautiful simplicity to the architecture of the Pantheon. The entry sequence passes through a large portico, a large set of double doors, and directly in to the vast rotunda. Originally there would have been a short flight of steps leading up to the portico; these were unfortunately removed when the ground in front of the Pantheon was raised, undoubtedly lessening the impact of the large portico as the threshold before the rotunda. The portico itself is constructed from Egyptian granite columns 11.9m tall with a diameter of 1.5m – relatively slender for a Roman Classical building, the Greek Classicism on which the architecture is based being more slender still. These columns hint at the might of the Empire at its peak: dragged over 100km from the quarry of Mons Claudianus to the Nile, taken by barge down the Nile, shipped across the Mediterranean Sea to Ostia, taken up the Tiber River to Rome, then dragged another 700m or so to the site of the Pantheon. This was Rome at a time of confidence and aspiration with resources to match. There are 16 columns in all forming the portico, all decorated with a Corinthian Capital. The pediment, now devoid of decoration, would once have been adorned with relief sculptures.
Beyond the portico and in to the rotunda, the extraordinary construction is made up of about 4500 tons of Roman concrete and has a coffered finish on the inside. The thickness of the dome varies from 6.4m at the base down to 1.2m at the oculus. Within the dome structure a number of hidden chambers reduce the weight of the roof, as does the oculus, and the roof is supported on eight barrel vaults. Geometrically the Pantheon is quite unique, with the height of the oculus matching the diameter of the dome at 43.3m – the interior would fit a sphere of that diameter in it perfectly. To give a rationale to these apparently random metric measurements, 43.3m is 150 Roman feet. The only source of light within the building is from the oculus, giving the church an inherently ‘heavenly’ orientation – an idea that is prevalent throughout later religious buildings.
I won’t dwell on the actual interior of the building in terms of tombs, sculpture, or art – the main attraction here is the rotunda itself. Such was the appeal of the vast dome that the great Renaissance architect Brunelleschi used the Pantheon as a model when designing the dome of the Basilica di Santa Maria del Fiore in Florence which has a dome of 44m diameter and upon completion heralded in new confidence in the construction of new architectures.
There is no charge to visit the Pantheon.
Appropriate clothing should be worn: knees and shoulders should be covered for both men and women. There is no need for women to cover their hair.