Which buildings did Michelangelo design or alter during his later years in Rome?

During his later years in Rome, Michelangelo focused increasingly on architecture, designing or altering several significant monuments to reflect the city's status as a world center. His major architectural projects in Rome included:1

• St. Peter’s Basilica: Serving as the head architect from 1546 until his death, Michelangelo discarded previous designs to revert to a plan featuring four equal cross arms. He was responsible for the design of the massive dome and performed significant construction work on the lower sections of the church, including the curving wall behind the altar.21
• Capitoline Square (Campidoglio): Commissioned by Pope Paul III, Michelangelo remodeled the existing city hall and designed two adjacent twin buildings. He also created a unique oval floor pattern to frame the statue of Marcus Aurelius, effectively reorienting the city's civic center.13
• Palazzo Farnese: Appointed to complete the palace after the death of Antonio da Sangallo in 1546, Michelangelo designed the balcony, the main cornice, the upper-story windows, and the upper story of the main courtyard.41

Additionally, he produced designs for other projects, such as the Porta Pia city gate and a church for the Florentine community in Rome, though these were either never fully realized or were significantly altered later.1