Final answer:
Bramante's concept for the interior of St. Peter's Basilica is characterized by a centralized plan with a Greek cross enclosed within a square and an enormous dome over the center.
Step-by-step explanation:
Bramante's concept for the interior of St. Peter's Basilica is characterized by the formal innovation of a centrally planned church in the shape of a Greek cross enclosed within a square with an enormous dome over the center. This design is known as a centralized plan, which differs from the traditional basilica plan with a longitudinal axis.
Furthermore, Bramante's original plan included smaller domes and half-domes radiating out from the central dome, creating a dynamic and interconnected space. While Raphael and Michelangelo made changes to Bramante's plan, his concept for a centralized space served as the foundation for the interior of St. Peter's Basilica.