<P> As it stands today, St. Peter's has been extended with a nave by Carlo Maderno . It is the chancel end (the ecclesiastical "Eastern end") with its huge centrally placed dome that is the work of Michelangelo . Because of its location within the Vatican State and because the projection of the nave screens the dome from sight when the building is approached from the square in front of it, the work of Michelangelo is best appreciated from a distance . What becomes apparent is that the architect has greatly reduced the clearly defined geometric forms of Bramante's plan of a square with square projections, and also of Raphael's plan of a square with semi-circular projections . Michelangelo has blurred the definition of the geometry by making the external masonry of massive proportions and filling in every corner with a small vestry or stairwell . The effect created is of a continuous wall - surface that is folded or fractured at different angles, but lacks the right - angles which usually define change of direction at the corners of a building . This exterior is surrounded by a giant order of Corinthian pilasters all set at slightly different angles to each other, in keeping with the ever - changing angles of the wall's surface . Above them the huge cornice ripples in a continuous band, giving the appearance of keeping the whole building in a state of compression . </P> <P> The dome of St. Peter's rises to a total height of 136.57 metres (448.1 ft) 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 41.47 metres (136.1 ft), slightly smaller than two of the three other huge domes that preceded it, those of the Pantheon of Ancient Rome, 43.3 metres (142 ft), and Florence Cathedral of the Early Renaissance, 44 metres (144 ft). It has a greater diameter by approximately 30 feet (9.1 m) 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 . </P> <P> 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 8 metres (26 ft) across which provides light to the interior . </P> <P> 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 . </P>

Who designed the dome of saint peter's basilica