What type of building was the pantheon?

Answer 1

The Pantheon was first built by Agrippa in 27 BC as part of a program of construction that was undertaken by Augustus. It burnt down in a big fire in 80 AD and was rebuilt by Domitian. It burnt down again in 110 AD and was rebuilt again by Hadrian.

The dome of the Pantheon is still the largest unreinforced concrete dome in the world. At its top there is a round opening which is called oculus (eye). Apart from the entry door, it is the only source of light as there are no windows. It also serves for ventilation and cooling. The rainwater which falls though it is drained by a network of drainage canals under the floor. The light from the oculus moves around the rotunda throughout the day, giving a reverse sundial effect.

The dome was built on top of a rotunda (round chamber) in concrete and was supported by a sophisticated system of relieving arches. Its downward thrust rests on eight vaults in the drum wall (which is 6.4 metres 21 ft. thick) and which are supported by eight piers. Its weight is carried by a ring of arches which form the oculus, which is 9.1 metres (30 ft.) in diameter. The dome weighs 5 short tonnes and is thickness is 6.4 metres (21 ft.) at the base and 1.2 metres (3.9 ft.) around the oculus. The weight of the dome was greatly reduced by (besides the lesser thickness at the top) using less dense stones in the higher layers and by having the top as the empty space of the oculus instead of an apex. If the same concrete had been used throughout, the downwards stress would have been 80% higher. The top of the rotunda which supports the dome has a series of relieving arches built into the brickwork which are visible outside. There are also relieving arches over the recesses on the inside. All these arches are hidden by the marble facing of the interior or by stone layering or stucco on the exterior. At the back of the temple there was a building to which the rotunda abutted, which helped to buttress the rotunda. There was no access to this building.

The interior of the dome has five rings of 28 coffers (sunken panels), which were evenly spaced. This kind of layout is difficult to achieve. The height form the floor to the oculus is the same as the diameter of the inner circle of the rotunda, 43.3 metres (142 ft.) Therefore, the interior would fit into a square.