TechnoTourist’s Engineering Expeditions

After being lost in the narrow streets of Rome, Italy, we finally emerged into a small square (Piazza della Rotonda) and saw the Pantheon! Famous for being the world's largest unreinforced dome, the Pantheon was commissioned in 126 AD by Emperor Hadrian. It's also well known for the large oculus, or opening, in the roof that exposes the Pantheon to the sky.

The Great Buildings website describes the construction of the Pantheon well:

"The dome is constructed of stepped rings of solid concrete with less and less density as lighter aggregate (pumice) is used, diminishing in thickness to about 1.2 m (4 feet) at the edge of the oculus. The dome rests on a cylinder of masonry walls 6 m (20 feet). Hidden voids and the interior recesses hollow out this construction, so that it works less as a solid mass and more like three continuous arcades which correspond to the three tiers of relieving arches visible on the building exterior. Originally, these exterior walls were faced with colored marbles."

The most commonly known features of the Pantheon are its portico, rotunda, and oculus. The granite columns of the portico were brought from Egypt. They were dragged 100 kilometers from the quarry and floated to Rome via the Nile River. Once in port they had to be dragged 700 meters to the site of the Pantheon. The height of the 60-ton columns is 39 feet and they are five feet in diameter.

The rotunda is supported by its thickness and honeycomb structure. There are no supporting beams inside the Pantheon; it's unreinforced. The dome is both 142 feet high and 142 feet in diameter. The oculus is approximately 30 feet in diameter. The building's bronze doors were melted down in the 17^th century - mainly to help fortify Castel Sant'Angelo.

The interior of the Pantheon has some beautiful architectural designs. The oculus and front door are the only source of light. No need to worry about the oculus exposing the Pantheon to the elements - a drain in the center of the floor takes care of any rainfall.

The Pantheon has had many uses over the centuries - temple to the Roman gods, Christian church, as a source of marble and bronze for other buildings, and a tomb. Artist Raphael is buried in the Pantheon as are other artists and Italian kings and a queen. Today it is still a tomb, a location for the Christian Mass, and a place for tourists to visit (for free) and learn about Rome's history.

Resources:

http://en.wikipedia.org/wiki/Pantheon,_Rome

http://www.greatbuildings.com/buildings/Pantheon.html