Mona Lisa mystery #1: Who was Mona Lisa?

Over the past century, it has been proposed that Mona Lisa was a noblewoman – Isabella d’Este, Marquise of Mantua, or Costanza d’Avalos, Duchess of Francavilla. Others have stared at that unsettling visage and seen the face of a man – Leonardo da Vinci himself, or the man who was for 20 years his assistant (and perhaps his lover), Gian Giacomo Caprotti. There is even a theory that the picture may have started out as a portrait from life but, over the years that Leonardo worked on it, evolved into an abstract vision of the feminine ideal.
These days, most experts agree that the Mona Lisa is a portrait of Lisa Gherardini del Giocondo, wife of a Florentine silk merchant named Francesco del Giocondo (hence the name by which she is known in Italy and France, La Gioconda, or La Joconde). When she sat for Leonardo da Vinci, in around 1503, she was about 24 years old. Her contrapposto pose – with the body angled away from the viewer, head turned forward – was widely admired and copied by Leonardo’s contemporaries. And his sfumato technique, where sharp edges are blurred to create an uncannily lifelike effect, was seen as a brilliant technical innovation, very unlike the slightly frozen human figures of earlier, lesser painters.
Mona Lisa mystery #2: The hidden initials

In 2010, Silvano Vinceti, chairman of Italy’s National Committee for Cultural Heritage, claimed to have discerned letters minutely painted on Mona Lisa’s eyes: L and V (Leonardo da Vinci’s initials) in the right eye, and perhaps C, E or B in the left. The Louvre responded that Vinceti’s letters were simply microscopic cracks in the paint.
Mona Lisa mystery #3: The broken backdrop

The distant, dreamlike vista behind Mona Lisa’s head seems to be higher on the right-hand side than on the left. It is hard to see how the landscape would join up. This is subliminally unsettling: Mona Lisa appears taller, more erect, when one’s gaze drifts to the left than when it is on the right.