Final answer:
Michelangelo designed the dome of St. Peter's Basilica, building upon the groundwork laid by Bramante and Sangallo the Younger.
Step-by-step explanation:
The dome of St. Peter's Basilica, the tallest in the world and a defining feature of this paramount religious structure, was designed by Michelangelo. Drawing upon the ideas and plans of Bramante and Sangallo the Younger, Michelangelo reshaped the concept and structure, which he began on or before 1564. It is Michelangelo's design, although he did not live to see its completion, that has had a lasting impact on architecture and remains awe-inspiring to visitors today.
Michelangelo designed the dome with two shells, instead of one. This was good for several reasons. A high dome looks good from the outside, but a lower dome looks better from the inside. The gap in between the domes has stairs so people can repair the dome. The space also helps to keep the inside shell dry so the decoration does not get damaged.