Architectural and Engineering Techniques
Arches were used to support the dome from the outside
-The dome was made of unreinforced concrete, so special support methods were needed to keep the dome from collapsing. Arches went around the dome to direct the weight of the dome to create downward thrust in order to keep the structure stable. The pressure from the thrust allowed for the weight of the dome to be spread evenly and anchor the entire building. The equal distribution of weight kept the dome from collapsing. These arches extended down to bays on the floor.
-The oculus is the 30 foot wide opening at the top of the dome. This serves as the Pantheon's light source. It also allows for ventilation so the room stays cool in summer. The dome in the Capitol Building in Washington DC has an "oculus" of sorts. It differs from the Pantheon in that its oculus is not an opening, but instead contains a painting. The dome in this building was modeled after the one in the Pantheon, which is why there is a circular area at the top. An opening was not needed as a light/ventilation source in the Capitol, so the ceiling is closed.
-Coffers (the arrangement of squares around the dome) were cut out to reduce the weight of the dome. This was yet another strategy used to ensure that the dome did not crush the building or collapse in on itself. The Capitol Building in Washington DC contains a similar coffering pattern.
-No cranes (polypastons) were used in the building process. Instead, scaffolding was used to get workers to the higher areas of the building.
-Travertine and basalt/lime cement were used on the lower areas. Pumice/lime cement was used on the dome as another way to reduce the weight. The lime/igneous rock cement mix was a stronger cement developed by the Romans. Because of this cement, the Pantheon has remained well-preserved for hundreds of years.
-The oculus is the 30 foot wide opening at the top of the dome. This serves as the Pantheon's light source. It also allows for ventilation so the room stays cool in summer. The dome in the Capitol Building in Washington DC has an "oculus" of sorts. It differs from the Pantheon in that its oculus is not an opening, but instead contains a painting. The dome in this building was modeled after the one in the Pantheon, which is why there is a circular area at the top. An opening was not needed as a light/ventilation source in the Capitol, so the ceiling is closed.
-Coffers (the arrangement of squares around the dome) were cut out to reduce the weight of the dome. This was yet another strategy used to ensure that the dome did not crush the building or collapse in on itself. The Capitol Building in Washington DC contains a similar coffering pattern.
-No cranes (polypastons) were used in the building process. Instead, scaffolding was used to get workers to the higher areas of the building.
-Travertine and basalt/lime cement were used on the lower areas. Pumice/lime cement was used on the dome as another way to reduce the weight. The lime/igneous rock cement mix was a stronger cement developed by the Romans. Because of this cement, the Pantheon has remained well-preserved for hundreds of years.
Who worked on the Pantheon?
Apollodorus designed the Pantheon, and oversaw its construction with Hadrian. Carpenters made the scaffolding. Most of the 700+ workers were stone masons. Their names can be found carved in the concrete bricks on the side of the building.