Many people describe the mystery of the Mona Lisa in many ways. Many say that the Mona Lisa is made in the style of Mr. Vinci's "mother". It is also said to be a picture of a pregnant woman (see Mona Lisa's hand-holding style and sitting style in the picture). Vinci's friend, happy that his wife was pregnant, asked Vinci to give her a picture of his wife. So Vinci drew the picture of Mona Lisa. Mon Lisa stands for "My Lady", which is why it's called Vinci's dream man.
Also a website called Paranormal Crucible claims the Mona Lisa is actually an alien creature.
There is also symbolism in the Mona Lisa film. For example- LV written in the eyes of Mona Lisa, 72, written in Italian- The Answer is of the year, besides many signs not understood.
Dan Brown claims in his book "The Da Vinci Code" that it is a mixed picture of men and women. Vinci on one side of her nose and a woman on the other side
Mona Lisa's smile on the other hand is actually an illusion. Mr. Vinci has drawn it in a geometric way in such a way that it looks like it is smiling and when approached it looks like it is sad.