The oculus at the top of the Pantheon lets in light (and everything else) that reflects inside the circular dome. The Pantheon was a wonder of the ancient city and became Brunelleschi's inspiration for the Duomo in Firenze (Florence).
A panoramic view of Rome from the cupola at the top of Saint Peter's Basilica.
The column of Marcus Aurelius in Piazza Colonna. This column has been standing in this spot since 193 CE.