Joachim Wtewael — Mars and Venus Surprised by Vulcan is the most erotic painting in the Mauritshuis. Vulcan caught his wife Venus in flagrante with Mars. He called the other gods to witness the adultery but the joke is on him rather than on the lovers. Cupid aims his arrow at Mercury, who is known to lust after Venus too. This is smut from 1601: painted on a sheet of copper allowed for details and for the painting to be handled for close-up inspection. It was long too risqué for public display.