The Prado Mona Lisa (School of Leonardo da Vinci, 1503) is far more than a simple copy—it is a crucial window into Leonardo’s workshop practice and the original appearance of the Mona Lisa. Painted alongside Leonardo da Vinci by one of his closest disciples, it mirrors the Louvre version with remarkable precision, suggesting both works were created simultaneously as part of a teaching exercise. Yet its greatest value lies in what time has preserved: unlike Leonardo’s panel, darkened by centuries of varnish and craquelure, the Prado version retains luminous greens, blues, and delicate transparencies that reveal a fresher, more vibrant vision of the composition. The landscape is clearer, the sfumato slightly less mysterious, and Lisa’s presence more immediate—all of which allow modern viewers to glimpse the chromatic richness and atmospheric clarity the original once possessed, making this painting indispensable for understanding Leonardo’s artistic methods and intentions.