The $500M art heist, unsolved

Left: Empty frames, from which thieves took "Storm on the Sea of Galilee" by Rembrandt (left background) and "The Concert" by Vermeer (right foreground), are seen on display in March 2010, at the Isabella Stewart Gardner Museum in Boston.

The paintings were among 13 works stolen from the museum on March 21, 1990, in what is considered the largest art theft in history. The thieves' take is estimated at perhaps $500 million -- and more than two decades later, the artworks have still not been recovered.

On March 18, 2013, the FBI announced it believes the burglars belonged to a criminal organization that removed the artwork to the Philadelphia area, and later offered it for sale about a decade ago.

Credit: AP Photo/Josh Reynolds