Leonardo da Vinci had begun working on a portrait of Lisa del Giocondo

Leonardo da Vinci had begun working on a portrait of Lisa del Giocondo, the model of the Mona Lisa, by October 1503. It is believed by some that the Mona Lisa was begun in 1503 or 1504 in Florence. Although the Louvre states that it was "doubtless painted between 1503 and 1506", art historian Martin Kemp says that there are some difficulties in confirming the dates with certainty.