License, verbatimCC0
The Metropolitan Museum of Art: Open Access, Creative Commons Zero (CC0). Flagged isPublicDomain=true in the museum's own record.
Cristofano di Michele Martini (Il Robetta). Hercules and the Hydra; wielding a torch he attacks the winged, multi-headed Hydra in rocky landscape, a hawk attacks a heron in the sky, ca. 1500–1520. The Metropolitan Museum of Art.