Las Meninas or The Family of Philip IV
"It’s a painting inside a painting, his teacher had said – look closely. Look here. Velázquez, the artist, is in the painting, at his easel, painting a painting, and what he’s painting is the king and queen, but they’re outside of the painting, where we are, looking in, and the only way we know they’re there is because we can see their reflection in a mirror directly in front of us. " (Orbital, p. 8)