The Pantheon is a temple that stands imposing and majestic in the centre of the city of Rome. It is one of the finest examples of ancient architecture. It is also one of the best preserved examples of ancient Roman architecture. The name Pantheon means "of all the Gods" and it was built by the Romans as temple in honor of all their Gods. 

The Pantheon is a circular building, with a great concrete dome rising from the walls. There is a front porch with Corinthian columns that support a gabled roof with triangular pediment. Beneath the porch are huge bronze double doors that measure twenty-four feet in height and which are the earliest known examples of this type.

Changes through the ages
The history of the Pantheon dates back to 27 B. C.. It was originally built by Marcus Vipsanius Agrippa. He probably constructed it as an ordinary classical temple. The temple was rectangular in shape, with a gabled roof that was supported by a colonnade on all sides. 

The temple building was later rebuilt by the Emperor Hadrian sometime between AD 118 and 128. In the year 123 AD, Hadrian built the great central space called the rotunda. The rotunda, rebuilt to a circular shape by the Emperors Septimius Lucius, Septimius Severus and Caracalla in the third century, forms the main part of the Pantheon. There is a magnificent portico that originally belonged to Agrippa's temple. Across the porch or the portico, there stand the sixteen great Corinthian columns. 

The Pantheon

The imposing dome
The Pantheon is renowned for its size, construction, and design. Until recent times, its dome was the largest ever built. It measures about one hundred and forty two feet (forty three meters) in diameter and rises to a height of seventy one feet (twenty two meters) above the base. There is no external evidence of brick arch support inside the dome, except in the lowest part. 

The exact method employed for its construction has not been determined. However, it is said that the quality of the mortar used in the concrete and the other materials that were used including basalt, brick, tufa (a stone formed from volcanic dust) and pumice were of very high quality. 

The uppermost part of the drum of the walls (seen from the outside) coincides with the lower part of the dome (seen from the inside) and it helps contain the thrust with internal brick

An inner view of the Pantheon dome 

arches. The drum itself is strengthened by huge brick arches and piers set above one another inside the walls, which are about twenty feet thick.