Lady with a Unicorn

The unicorn is a symbol of chastity — it could only be tamed by a virgin. The sitter's identity has been debated for centuries (Giulia Farnese? Maddalena Strozzi? An unknown Roman bride?). X-rays reveal the picture began as a portrait with a dog, was overpainted with a unicorn, and then further overpainted in the 17th century to turn her into St. Catherine — before conservators returned it to Raphael's second version.