Pantheon, a temple of ancient Rome. It survives in the best state of preservation of any building in Rome dating from the days of the Empire. The building is a rotunda(a circular structure), covered by a half-sphere dome. Across the front of the building is a colonnaded portico with a gable roof and pediment in classical style. The columns of the portico and the interior have Corinthian capitals.

The building is constructed of brick and concrete. The interior of the rotunda is 142 1/2 feet (43.4 m) in diameter. The dome, one of the largest in the world, is also 142 1/2 feet in inner diameter and the same measurement from inner crown to floor.

The original Pantheon was built in 27 B.C. by Agrippa, son-in-law of the emperor Augustus, as a shrine to all the gods. It was damaged by fire in 80 A.D. and the emperor Domitian made extensive restorations. The Pantheon was rebuilt in its present form by the emperor Hadrian between 118 and 128 A.D. The inner walls were originally faced with white marble below and finished in stucco above. The outside of the dome was covered with gilded bronze plates, and the bronze doors were plated with gold.

In 609 the temple became the Christian church of St. Mary of the Martyrs, and the bones of Christian martyrs were moved to it from the Catacombs. It is now called St. Mary Rotunda.