3 Best Sights in Aventino and Testaccio, Rome

A former monastery, founded in the 7th century by monks fleeing Jerusalem following the Arab invasion, this is a major monument of Rome, though it takes on a subdued air thanks to its modern quiet surroundings in the upscale San Saba district. The serene but rustic interior harbors 10th-century frescoes, a famed Cosmatesque mosaic floor, and a hodgepodge of ancient marble pieces.

This Early Christian basilica is stark and tranquil, showing off the lovely simplicity common to churches of its era. Although some of the side chapels were added in the 16th and 17th centuries, the essential form is as Rome's Christians knew it in the 5th century. Most striking are the 24 fluted Corinthian columns that line the classical interior. Once bright with mosaics, today the church has only one above the entrance door (its gold letters announce how the church was founded by Peter of Illyria, "rich for the poor," under Pope Celestine I). The beautifully carved, 5th-century cedar doors to the left of the outside entrance are the oldest of their kind in existence.

Once a part of the Aurelian Walls and now a part of the Cimitero Acattolico, this monumental tomb was designed in 12 BC for the immensely wealthy praetor Gaius Cestius, in the form of a 120-foot-tall pyramid. According to an inscription, it was completed in a little less than a year. Though little else is known about the Roman official, he clearly had a taste for grandeur and liked to show off his travels to far parts of the nascent empire. The pyramid was restored in 2015 thanks to a €1 million donation from Japanese fashion tycoon Yuzo Yagi. Guided visits (when available) require a reservation but are usually on the second and fourth Saturday of each month.