Introduction The Pantheon has long had iconic status, universally acknowledged as the greatest achievement of Roman architecture and one of the wonders of the Roman world. The unparalleled clear span of the dome particularly impressed later architects and engineers, who used it as a point of reference for their own wide-span structures, including the domes of Santa Maria del Fiore in Florence, St. Peter’s in Rome and St. Paul’s in London, and even the great Victorian train sheds of St. Pancras Station. A major part of the universal fascination with the building lies in its complex structural system and the constructional processes employed, particularly in relation to the dome. Because of the difficulties we have with understanding the Pantheon as a structure, it has been natural to imagine that it was also an exceptionally difficult, time-consuming, and labor-intensive construction project for the Romans. The aim of this chapter is to test some of these assumptions, using a method of reverse quantity surveying, originally developed for the Baths of Caracalla in Rome. This can provide a rough estimate of the minimum manpower requirements for the actual construction on site (excluding all labor relating to the production, supply, and transportation of materials to the site), as well as the minimum construction period. Although the calculations can yield only approximate and hypothetical minimum figures, they at least provide an idea of the scale of the project in terms of manpower, and allow us to test whether this really was the “mammoth undertaking” assumed by many scholars. This also has implications for how we see the Pantheon as part of the building projects of Trajan and Hadrian.
