herowyn:

The theft and return of Mona Lisa

On 21 August 1911, the painting was stolen from the Louvre. The theft was not discovered until the next day, when painter Louis Béroud walked into the museum and went to the Salon Carré where the Mona Lisa had been on display for five years, only to find four iron pegs on the wall.

Two years later the thief revealed himself. Louvre employee Vincenzo Peruggia had stolen the Mona Lisa by entering the building during regular hours, hiding in a broom closet, and walking out with it hidden under his coat after the museum had closed.