Pinacoteca di Brera — Milan, Lombardy, Italy

Apparently the colours aren't random: her pale blue and his red were meant to echo the flags of the alliance fighting Austria at the time this was painted. Some readings even spot a dagger half-hidden in his cloak — less a lover saying goodbye, more someone about to go do something dangerous.

The story goes that he kept this one — it was still in his studio when he died, and his sons sold it off to clear what he owed. No one's settled on when he painted it either; the guesses spread across a couple of decades.