Final answer:
The altar wall in the Sistine Chapel once displayed Perugino's 'Nativity', differentiating it from other works such as Michelangelo's Pieta, which is in St. Peter's Basilica.
Step-by-step explanation:
The altar wall in Sistine Chapel once displayed Perugino's 'Nativity'. The Sistine Chapel, known for its magnificent ceiling and the Last Judgment mural painted by Michelangelo, is located in Vatican City. It is a renowned site of artistic and religious significance, where Perugino and Botticelli, among others, contributed frescoes. Although Michelangelo's Pieta and his design for the dome are associated with St. Peter's Basilica, and not the Sistine Chapel, it's essential to differentiate between the artworks and their specific locations when considering Renaissance art.