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 Sintes, after Nicola Michetti (attributed to). The Prima Macchina for the Chinea of 1733: Parnassus with Apollo and the Muses, 1733. National Gallery of Art, Washington.