Visit Santa Maria Maggiore (St. Mary Major) if only to see Bernini's magnificant staircase! There are 80 churches in Rome dedicated to Mary. This is the largest and considered the most important, thus, the label "maggiore". Along with St. Peter's, St. John's and St. Paul's, this is one of four papal basilicas in Rome. Dating back to the 5th century, Santa Maria Maggiore has a spectacular interior, with ornate chapels and a gilded ceiling. Admission is free. It is easy to reach, with several metro stops in the vicinity. This is a good place to visit if you are picking up Papal Audience tickets at the Church of Santa Susanna, which is nearby.