One of the most important architectural projects of the entire Renaissance is the construction of the spectacular dome atop the church of Santa Maria del Fiore, Florence Cathedral, by Filippo Brunelleschi (1377-1446). In the inner shell of the octagonal structure, the vertical ribs display a pointed fifth curvature, whose radius is equal to 4/5 of the diagonal of the base octagon. The work, begun in the summer of 1420, was finished - except for the lantern - by 1436. The dome was built without the use of a wooden centering to support the masonry. To carry out the project successfully and convince his skeptical fellow-Florentines, Brunelleschi devised several boldly innovative solutions that served three crucial purposes: to lighten the massive structure; to set up a worksite organization that could efficiently handle each successive construction stage; and to ensure the stability of the brickwork courses, whose inward slope increases continually from the base to the dome's closing stone ring, called the oculus (the "eye").