Whether the name refers to the number of deities honoured in the temple or means "very holy" is uncertain but this is one of the best preserved of all ancient roman buildings and the best preserved in Rome. The Pantheon was a temple which enhanced even further the remarkable group of buildings erected by Agrippa in the Field of Mars, campus Martius, name still in use today.

According to the inscription on the frieze of the pronaos the temple was built in 27 B.C. It seems probable, especially after the battle of Actium where Cleopatra and Marc Anthony were defeated by Octavian, that the temple was built for the glorification of the gens Iulia, and that it was dedicated in particular to Mars and Venus, the most prominent among the ancestral deities. The Pantheon of Agrippa burned in 80 A.D. and was later restored by Domitian and in the reign of Trajan. The restoration by Hadrian carried out after 126 was in fact an entirely new construction, for even the foundations of the existing building date from that time. The building is circular, with a portico of granite columns, opening into the coffered dome - the largest ever built in concrete - with a central bull's eye open to the sky.

Regarded as a source of inspiration for all the domes built ever after the Pantheon since the 7th century has been used as a Roman Catholic church dedicated to "St. Mary and the Martyrs". Although statues of deities had been therefore replaced by christian art the overall remodelling did not manage to alter the original appearance. Inside amongst beautiful works of art are also the tombs of the first two italian kings and the tomb of the great artist Raphael.