An early 3rd century sarcophagus depicting Rhea Silvia, reclining, being approached by the god Mars. She will conceive the twins Romulus and Remus. This legendary scene has been depicted many times in art. You’ll find multiple depictions (in marble, painting, on an ancient coin) here in the Gallery.
I like this depiction, as it shows the seated goddess Vesta to the right of her priestess. Some people believe this seated figure is Venus, but to me the figure looks far more like Vesta who, we can assume, understands the significance of this union and is thus permitting it.
Giovanni Dall'Orto via Wikimedia Commons.