That would be Michelangelo (full name Michelangelo di Lodovico Buonarroti Simoni). He painted the Sistine Chapel for roughly four years (1508 - 1512) when he was invited back to Rome by Pope Julius II to build the Pope's Tomb. The St. Peter's Basilica was something he succeeded from Antonio da Sangallo the Younger as an architect. He changed the design so that the western end finished with his design, as with the dome.