128: The Pantheon – Rome, Italy

  

Innovation: Pantheon
Location: Rome, Italy
Year: 128 AD
By: Publius Aelius Hadrianus

The Pantheon was built in 128 AD as a temple to all the Gods of Ancient Rome. All the materials used in construction were floated down the Tiber and taken to site using carts using animals and the lighter materials were taken by men. The layout is such that there is a rectangular entrance connected to a circular enclosure. The dome is built so that it would remain robust under its own weight using no steel reinforcing rods to resist cracking; it still remains the largest unreinforced concrete dome till today. The giant concrete dome is 142 feet in diameter which contains a 25 feet oculus at the highest point which is the only point that light can pass through. The concrete at the top is lighter than normal density and much heavier at the base. The internal part of the dome is made up of coffers, which are rectangular panels sunken into the structure to help lighten the weight. The oculus at the top decreases the overall weight and distributes the stress around its circumference. The condition of the terrain was not one that could easily be built upon. To ensure the building would not fall the builders built a second concrete ring foundation to hold the first and put buttress walls on the side opposite the porch to keep cracks from extending.  `

Source: 1, 2