Uffizi: The Annunciation by Leonardo da Vinci

The Annunciation was a favourite subject of many artists in the Renaissance depicting the moment when Archangel Gabriel descends to Earth to tell Mary she will bear a child. This version is an example of very early Leonardo, which is perhaps why the painting is actually finished, seeing as Da Vince was notorious for never finishing his works! His later involvement with science meant that he was far too distracted to ever complete his paintings.