Basilica di San Saba
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.