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. Remains of the Temple of Castor and Pollux . . . (Avanzo del Tempio di Castore e Polluce . . .), 18th century. The Metropolitan Museum of Art.