ROME: The Pantheon

When you think of Rome, images of the Colosseum, and the Vatican come to mind. As old as these buildings may be, the oldest surviving Roman building that is still in use today is the Pantheon. Named from the Greek meaning 'to every god', it was commissioned by Marcus Agrippa as a temple to all the gods of Ancient Rome, and rebuilt by Emperor Hadrian in about 126 AD.

At the top of the dome is a large opening, known as the oculus, which was the only source of light.

The front portico has three rows of 8 columns, each one with a diameter of 1.5m. Amazingly, each of these monolithic columns is cut from a single piece of marble.

The history of the Pantheon

The construction of the Pantheon was part of a program of construction that was undertaken by Augustus Caesar and his supporters. Together, they built more than twenty structures on the Campus Martius, including the Baths of Agrippa and the Saepta Julia.

It had long been thought that the current building was built by Agrippa, with later alterations undertaken, and this was in part because of the inscription on the front of the temple.

The inscription across the front of the Pantheon says: 

M·AGRIPPA·L·F·COS·TERTIVM·FECIT 

or in full,

"M[arcus] Agrippa L[ucii] f[ilius] co[n] s[ul] tertium fecit," 

meaning "Marcus Agrippa, son of Lucius, made this building when consul for the third time."

However, archaeological excavations have shown that the Pantheon of Agrippa had been completely destroyed except for the facade, and Emperor Hadrian was responsible for rebuilding the Pantheon on the site of Agrippa's original temple.

The Interior

Originally a temple for all pagan gods, the temple was converted into a church in 609.

The Pantheon now contains the tombs of the famous artist Raphael and of several Italian Kings.

Its ecclasiastic interior design contrast with the temple's structural design.

However, the marble floor - which features a design consisting of a series of geometric patterns - is still the ancient Roman original. 

Probably one of the most fascinating features of the Pantheon is the Architecture. The structure of the Pantheon is comprised of a series of intersecting arches. The arches rest on eight piers which support eight round-headed arches which run through the drum from its inner to its outer face. 

The arches correspond to the eight bays on the floor level that house statues. The dome itself is supported by a series of arches that run horizontally round. Romans had perfected the use of arches which helped sustain the weight of their magnanimous buildings.

The Rotunda

The rotunda is perhaps the most striking element of the pantheons architecture. In fact it was the largest dome in the world until 1436 when the Florence Cathedral was constructed.


The thickness of the dome varies from 6.4 metres (21 ft) at the base of the dome to 1.2 metres (3.9 ft) around the oculus.

The stresses in the dome were found to be substantially reduced by the use of successively less dense aggregate stones, such as small pots or pieces of pumice, in higher layers of the dome.

Hidden chambers engineered within the rotunda form a sophisticated honeycomb structure. 

This reduced the weight of the roof, as did the elimination of the apex by means of the oculus. The top of the rotunda wall features a series of brick relieving arches, visible on the outside and built into the mass of the brickwork. 

The Pantheon is full of such devices – for example, there are relieving arches over the recesses inside – but all these arches were hidden by marble facing on the interior and possibly by stone revetment or stucco on the exterior.

The height to the oculus and the diameter of the interior circle are the same, 43.3 metres (142 ft), so the whole interior would fit exactly within a cube.

These dimensions make more sense when expressed in ancient Roman units of measurement: 

The dome spans 150 Roman feet; the oculus is 30 Roman feet in diameter; the doorway is 40 Roman feet high.

The Pantheon still holds the record for the world's largest unreinforced concrete dome. It is also substantially larger than earlier domes. Though often drawn as a free-standing building, there was a building at its rear into which it abutted. While this building helped buttress the rotunda, there was no interior passage from one to the other.

Based on an article from http://en.wikipedia.org/wiki/Pantheon,_Rome and http://www.aviewoncities.com/rome/pantheon.htm
Photos are from my Roman holiday 2011 and http://scienceman2008.blogspot.co.uk/