Watch The Secret Mona Lisa for Free: How to Stream the Movie Online at 123Movies. . The Mona Lisa by the Italian Renaissance artist Leonardo da Vinci is the most famous painting in the world. What is the secret behind the "real" Mona Lisa? It draws legions of visitors to the Louvre in Paris to contemplate her enigmatic expression. In this "detective story," historians tell us how Leonardo developed the painting and uncover the long-hidden identity of the smiling woman.