Described by an English visitor, in 1549, as ‘the perfectest of all the antiquities’, the Pantheon is the grandest and best-preserved monument of ancient Rome.
A great deal of mystery surrounds the Pantheon; its age, even its name is open to doubt. Most scholars think it was built between 118 to 128 CE, during the reign of the emperor Hadrian (r. 117-38). Whatever the case may be, it remains the most perfectly preserved temple from classical antiquity.
The Pantheon stands on the site of a temple built by Marcus Vipsanius Agrippa (63-12 BCE), general, close friend and son-in-law of the emperor Augustus (r. 27 BCE-14 CE). It was completed in either 27 or 25 BCE. A century or so later, in 80 CE, it was damaged by fire and restored by the emperor Domitian (r. 81-96). It was struck by lightning and burned again in 110 before being rebuilt in its present form.
The monolithic granite columns in the portico are 40 feet (12 m) high and weigh 50 tonnes apiece. The granite was quarried in Egypt.
The Pantheon's concrete dome is the largest of its kind in the world. Its internal diameter is 43.3 m (142 ft), which is exactly the same as the height from the pavement to the nine-metre wide oculus. The dome, which sits on a six-metre-thick wall, is made up of five rings, each comprising 28 coffers, which diminish in size as it rises. The thickness of the dome also decreases as it rises; at its height it is roughly two metres thick. The exterior of the dome was originally covered in gilded bronze tiles; they were plundered in 663 by the Byzantine emperor Constans II (r. 641-68). The dome was later covered with lead tiles.
When the Pantheon was completed, and for reasons unknown, an inscription to Marcus Agrippa was placed above the portico. For centuries, this led people to think the temple was a much older building. The inscription reads: M · AGRIPPA · L · F · COS · TERTIVM · FECIT (Marcus Agrippa, son of Lucius, built this in his third consulship). At some point the original gilded bronze letters disappeared, but the empty matrices of the inscription made it possible to work out what had once been written. In 1894 the hollows were filled with new letters.
There is a second, and much smaller, inscription: IMP · CAES · L · SEPTIMIVS · SEVERVS · ET · IMP · M · AVRELIVS · ANTONINVS · PANTHEVM · VETVSTATE · CORRVPTVM · CUM · OMNI · CVLTV · RESTITVERVNT (Emperor Septimius Severus and Emperor Aurelius Antoninus restored the worn-out Pantheon to elegance). The great bronze doors of the Pantheon are thought to be the oldest in Rome.
In 609, the Pantheon was converted into a church, that of Sancta Maria ad Martyres, also known as Santa Maria Rotonda. In time, a small bell tower was added to the apex of the pediment. In the 17th century, Pope Urban VIII (r. 1623-44) had this replaced by twin bell towers (often mistakenly attributed to Bernini), which were nicknamed the 'orecchie d'asino' (ears of an ass). The bell towers were removed in 1883.
The Pantheon is the final resting-place of the Renaissance artists Raphael (1473-1520) and Baldassare Peruzzi (1481-1536), the Baroque composer Arcangelo Corelli (1653-1713), and the first two kings of Italy Vittorio Emanuele II (r. 1861-78) and his son Umberto I (r. 1878-1900).
The Venerable Bede (c. 673-735), the English monk and historian, claimed the Pantheon was the work of the Devil; the oculus, he asserted, was created by demons escaping when the temple was consecrated as a church.