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. Elevation and plan of the second-order portico at the Theater of Marcellus (Teatro di Marcello), Rome, from "Le Antichità Romane", 1756. The Metropolitan Museum of Art.