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. Veduta degli avanzi del Castro Pretorio nella Villa Adriana a Tivoli (View of the Remains of the Praetorian Fort [the Poecile], Hadrian's Villa, Tivoli), 1770. The Metropolitan Museum of Art.