License, verbatimCC0
The Metropolitan Museum of Art: Open Access, Creative Commons Zero (CC0). Flagged isPublicDomain=true in the museum's own record.
Giovanni Battista Piranesi. The Forum Romanum, or Campo Vaccino, from the Capitol, with the Arch of Septimius in the foreground left, Temple of Vespian right, and the Colosseum in the distance (Veduta di Campo Vaccino), ca. 1775. The Metropolitan Museum of Art.