Although the inscription that welcomes visitors attributes the construction of the Pantheon to Marcus Agrippa, son-in-law of the emperor Augustus, the version of the temple that we admire today was built under the reign of Hadrian circa 150 years later.
The previous temple was rectangular and overlooked an ample plaza. The project to build a place of worship of all the gods of the Olympus was comprised in a broader plan to enhance the Campus Martius, conceived by Augustus after the conquest of Egypt.
Situated near the Baths of Agrippa, the Pantheon was inaugurated around BC 25 and was part of a religious complex also comprising Septa Iulia and the Temple of Neptune.
The Augustan Pantheon was rebuilt after a devastating fire destroyed it in AD 80. The audacious project of the largest dome of antiquity originated from Hadrian and his architect Apollodorus of Damascus, in AD 125. Belonging to the Augustan Pantheon are some of the columns of the portico and the two niches which probably housed the statues of Agrippa and Augustus.
Over time the Pantheon suffered many spoliations, especially during the papacy of Urban VIII, who had the bronze ceiling of the portico melted to create the bladachin above the main altar of St. Peter’s Basilica and make the bombards of Castel Sant’Angelo. If the building is largely intact it is due to its conversion into a Christian a church in the 7th century and consecration to St. Mary and the Martyrs. It is still a consecrated church where masses and weddings are celebrated. It houses illustrious tombs, such as those of Raphael Sanzio, Annibale Carracci, Victor Emanuel II King of Italy and Queen Margherita. The fresco by Melozzo da Forlì depicting the Annunciation is one of the exquisite works of art that adorn the Pantheon’s interior.
The dome once covered the area of the square in front of the ancient Pantheon. Its diameter is the largest that could be achieved without risking its collapse: 43.44 metres, the same distance from the floor to the circular opening of the dome. This means that a sphere of the same diameter would fit perfectly under the dome.
The centre of the floor is pierced by holes to allow the rain water to drain. In ancient times the rain would not enter the temple due to the many lit candles, which would raise the temperature inside. This was hailed as a miracle by the faithful.