It is neither ellipse nor parabola nor section of the circle, but an inspiration of creative fancy.

It outsoars in vital force, in elegance of form, the dome of the Pantheon and the dome of Brunelleschi, upon which it was actually modelled.

As a French architect, adverse to Michelangelo, has remarked: "This portion is simple, noble, grand.

It is an unparalleled idea, and the author of this marvellous cupola had the right to be proud of the thought which controlled his pencil when he traced it." An English critic, no less adverse to the Italian style, is forced to admit that architecture "has seldom produced a more magnificent object" than the cupola, "if its bad connection with the building is overlooked." He also adds that, internally, "the sublime concave" of this immense dome is the one redeeming feature of S.Peter's.
Michelangelo's reputation, not only as an imaginative builder, but also as a practical engineer in architecture, depends in a very large measure upon the cupola of S.Peter's.

It is, therefore, of great importance to ascertain exactly how far the dome in its present form belongs to his conception.