The Pantheon, 125 AD, Rome, Italy

The Pantheon was the greatest dome structure built during the Roman Empire and the architect of this project was Apollodorus of Damascus. The structure relates to the Treasury of Atreus in Egypt built 1,400 years before the Pantheon. Also, the Greeks and Romans had built numerous circular buildings, the one closest to the Pantheon is the Arsinoeion, a tholos dedicated to the great god in c.270 BC on the island of Samothrace in the northern Aegean. The Pantheon was built on the exact site of two earlier Pantheon buildings, one commissioned by Marcus Vipsanius Agrippa (27-25 BCE) and the second by Domitian. The first was destroyed by fire in 80 CE and the second was struck by lightning in 110 CE and again burned down. The third Pantheon was probably begun in the reign of Trajan (98-117 CE) but not finally finished until around 125 CE when Hadrian was emperor. The Pantheon was first built as a temple to all gods, which is why the dome span to 142 feet. The perfectly balanced proportions of the interior are since the inner diameter of the dome is exactly equal to the height of its oculus from the floor.

Treasury of Atreus

Pantheon

The actual construction of the building was complex and original: with inspirations from other structures. There's a series of six constructional layers, starting with the heaviest for the foundations and finishing with the lightest, pumice, for the upper portion of the dome. The seventh layer consisting simply of air, since the top of the dome is open to the sky through an oculus 28 feet in diameter.

The whole building stands on a 1.3 meters high base which originally extended a further 7 meters in front of the colonnade. The building consists of two principal parts - the porch, which is very Classical Greek in presentation, and the circular main building which is much more Roman in style. The circular building is built with brick and concrete but was originally faced with white marble stucco to match the porch in appearance.

The interior of the Pantheon may well be the first building from Classical architecture where the interior is deliberately made to outshine the exterior. The dome is made from mix of concrete and its interior is further lightened by five rings of 28 coffers which reduce in size as they rise towards the center of the dome. The Pantheon was beautifully engineer for the religious purpose it has, which was to all the Gods.

Source:

Cartwright, Mark. "The Pantheon, Rome." Ancient History Encyclopedia. 09 June 2013. Web.

Glancey, Jonathan. Architecture. London: DK, 2006. PrintWatkin, David. A History of Western Architecture. Sixth ed. New York: Thames and Hudson, 1986. Print.