MONA LISA AND HER SISTER. Two Coin Set with Original Gem Stones! Second Jewels of Art Set The Mona Lisa at the Prado in Madrid was thought to be just another fine copy, with added eyebrows and an odd black background. But curators at Spain's national art museum announced a startling discovery: the painting was actually executed by an artist in Leonardo da Vinci's workshop at the same time as the original. Conservators believe the artist could be Francesco Melzi, one of Leonardo's favorite pupils. The Mona Lisa is widely believed to be a portrait of Lisa Gherardini, a Florentine merchant's wife, and the copy makes her look younger and more seductive.