Filippo Brunelleschi, born in Florence in 1377, worked primarily as an architect, but he was also a goldsmith, sculptor and mathematician. His major work is the Dome of the Cathedral of Santa Maria del Fiore in Florence, known familiarly as "The Duomo." Brunelleschi was the first person to determine the geometrical laws of linear perspective; his discoveries borne out by his successful creation of the great dome. The research found in this book thus marks a turning point in our knowledge of how the dome was built, as it is fruit of a new campaign of investigation that employed the most recent technologies in the areas of survey and diagnostics. The results are of great interest since, with a few exceptions, all the theories developed by scholars over the centuries had come up with almost the identical geometric model. This is significant, since it shows that all scholars, even if they employed different methods and vocabulary independently and unaware of each other, have given the same answer to the same problem. It was against this background that we began a systematic survey of the structure, with special attention to the masonry fabric of the Dome.