St. Peter 's Basilica is the largest of all Roman Catholic churches and by any standards a grandiose achievement , but it inevitably suffered from the competing visions of all the architects called in to collaborate Bramante , Giuliano da Sangallo , Raphael , Baldassare Peruzzi , Michelangelo , Giacomo Della Porta , Domenico Fontana , and Carlo Maderno each adding , subtracting , and modifying , often with a pope looking over his shoulder .
Collaborating architects ' competing visions ultimately harmed the Basilica .