“The Greek word pantheion means ‘temple of all the gods,’ which makes the building polytheistic. Cassius Dio, a Greco-Roman senator writing some seventy-five years after the present Pantheon was built, opined, ‘It has this name … because its vaulted roof resembles the heavens.’
In the audacity and thoroughness of its engineering, in the grand harmony of its proportions, and in the eloquent weight of history with which it is imbued, the Pantheon is certainly the greatest of all surviving structures of ancient Rome. The Colosseum exceeds it in mass and size, but it is the form of the Pantheon that elicits one’s amazement: that huge dome, opened at the top by an oculus which seems not merely to show but to admit the sky, is a landmark in the history of construction and, one might add, of architectural metaphor. Even today, almost two millennia after it was finished, the alert visitor is likely to be struck less by its great age than by its inexhaustible newness. This is truly Roman architecture, not Greek. Greek building was a matter of straight posts and straight lintels. The Roman genius was to conceive and build three-dimensional curved structures, of which the Pantheon’s dome is the sublime archetype. This could not be done, at least not on a larger scale, in hewn stone. A plastic, moldable substance was needed, and the Romans found it in concrete, whose use was unknown to Greek architecture.
The statistics, bare as they are, remain. With a diameter of 43.3 meters, its dome is the world’s largest in unreinforced concrete, surpassing the diameter of Saint Peter’s cupola by just seventy-eight centimeters. There are larger domes on earth, but they are segmental and reinforced with steel, like the hundred-meter dome of the 1960 Palazzetto dello Sport in Rome. No modern architect would dare to attempt another Pantheon using the same structural principles—nobody would insure it. But the Pantheon has stood for nearly two thousand years and shows no prospect of collapse.”
From Robert Hughes’ Rome. - 20 minutes ago