successive and final designs The dome of St. Peter's rises to a total height of from the floor of the basilica to the top of the external cross. It is the tallest dome in the world. Its internal diameter is , slightly smaller than two of the three other huge domes that preceded it, those of the Pantheon of Ancient Rome, , and Florence Cathedral of the Early Renaissance, . It has a greater diameter by approximately than Constantinople's Hagia Sophia church, completed in 537. It was to the domes of the Pantheon and Florence duomo that the architects of St. Peter's looked for solutions as to how to go about building what was conceived, from the outset, as the greatest dome of Christendom. Bramante and Sangallo, 1506 and 1513 The dome of the Pantheon stands on a circular wall with no entrances or windows except a single door. The whole building is as high as it is wide. Its dome is constructed in a single shell of concrete, made light by the inclusion of a large amount of the volcanic stones tuff and pumice. The inner surface of the dome is deeply coffered which has the effect of creating both vertical and horizontal ribs while lightening the overall load. At the summit is an ocular opening across which provides light to the interior. Bramante's plan for the dome of St. Peter's (1506) follows that of the Pantheon very closely, and like that of the Pantheon, was designed to be constructed in Tufa Concrete for which he had rediscovered a formula. With the exception of the lantern that surmounts it, the profile is very similar, except that in this case, the supporting wall becomes a drum raised high above ground level on four massive piers. The solid wall, as used at the Pantheon, is lightened at St. Peter's by Bramante piercing it with windows and encircling it with a peristyle. In the case of Florence Cathedral, the desired visual appearance of the pointed dome existed for many years before Brunelleschi made its construction feasible. Its double-shell construction of bricks locked together in a herringbone pattern (re-introduced from Byzantine architecture), and the gentle upward slope of its eight stone ribs made it possible for the construction to take place without the massive wooden formwork necessary to construct hemispherical arches. While its appearance, with the exception of the details of the lantern,