License, verbatimPD
The National Gallery of Art: open access image with no usage restrictions under the NGA's open access policy (openaccess=1 in the Gallery's published_images dataset).
Giovanni Battista Pittoni, after Hieronymus Cock. Colossaei. Ro. Prospectus. 3 (Third View of the Colosseum in Rome), c. 1561. National Gallery of Art, Washington.