The Pantheon is said (and quite rightly so) to be the best preserved Roman building in the world.) Originally constructed in 27BC by Augustus' right-hand man Agrippa, the Pantheon was a temple dedicated to all the Gods of Rome and formed part of a large complex that also included a huge bath house, lake and nymphaeum. The inscription above the facade reads M.AGRIPPA L: F: COS TERTIVM FECIT (Marcus Agrippa, son of Lucius, made this in his 3rd Consulate), though the inscription actually dates from the time of Hadrian when the entire building was reconstructed. It's current form dates from that rebuild. The original south-facing rectangular building of Agrippa burned in 80 AD, being restored by Domitian, with a later complete rebuild (north-facing) in a different form by Hadrian. The Pantheon may have been restored again by Antoninus Pius, and certainly was by Septimius Severus.

The circular Pantheon with its rectangular frontage is one of Rome's most recognisable buildings. Almost the entire original building with decoration survives. The doors are believed to be the original Hadrianic ones, the granite columns are original, even the roof (a huge, 140ft unsupported dome) is original. The roof is a masterpiece of engineering, built in a series of rings of different materials that weigh less than those below. The centre of the dome is hollow, leaving a light well open to the sky through which rain pours or sun shines onto the marble floor. The bronze doors that can be seen today are original from the Hadrianic edifice (with some later repairs) and though the bronze facing of the ceiling was removed by Constantius II in 663, Gregory III had the roof leaded to protect it.

In 608AD the Eastern Emperor Phocas donated this temple to the Pope and it became a church which it remains to this day.

Access: The Pantheon is open during church hours and is visible externally in the Piazza della Rotonda.