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 so-called Villa of Maecenas at Tivoli. Interior with two figures in the opening of an arch above. (Veduta interna della Villa di Mecenate), ca. 1764. The Metropolitan Museum of Art.