The mystery of "Who was Mona Lisa?" has now been solved.
Many art historians have speculated that Da Vinci’s model was Lisa Gherardini, the wife of a wealthy Florentine merchant named Francesco del Giocondo (which is why Europeans refer to the painting as "La Giaconda"). But that was just a guess.
Recent notes from Leonardo himself have been uncovered and translated, and the mystery is solved. Turns out the historians were right.