The Dome: Construction on the dome, one of the most ambitious architectural and engineering feats of its time, had been stalled for some time because it was determined that building a cupola of that size would be impossible without the use of flying buttresses. Brunelleschi, however, had a deep knowledge and understanding of the key concepts of physics and geometry and therefore was able to solve this dilemma. His brilliance ultimately won him the challenge.Brunelleschi's controversial and innovative plans provided for inner and outer shells that were held together with a ring and rib system, as well as employed a herringbone pattern to keep the bricks of the dome from falling to the ground. These construction techniques are commonplace today but were quite revolutionary during the time it was erected.Work on the dome began in 1420. Crowned by a lantern with a conical roof, the dome wasn't completely finished until after Brunelleschi's death in 1446. A gilt copper sphere and cross containing holy relics were designed by Andrea del Verrocchio and added in 1466. Between 1572 and 1579, a fresco of The Last Judgment was painted on the inner shell of the dome—started by Giorgio Vasari and finished by Federico Zuccari.