The Isabella Stewart Gardner Museum Heist occurred on March 18, 1990, when two men disguised as police officers gained entry to the museum in Boston. They tied up the guards and stole 13 pieces of art valued at around $500 million, including works by Vermeer, Rembrandt, and Degas. Despite extensive investigations, the stolen artworks have never been recovered, making it one of the largest art thefts in history. The museum still displays empty frames where the stolen pieces once hung, serving as a reminder of the crime and the ongoing mystery surrounding the missing masterpieces.