We'll take a closer look at some well-known paintings and reveal their amazing secrets hidden in plain sight for hundreds of years. Read on to hear music hidden in a 500-year-old picture, speculate on what a medieval UFO may have looked like, and see if you can find the self-portrait hidden inside a painting.

On March 18th, 1990, two men disguised as police officers entered the Isabella Stewart Gardner Museum in Boston, USA and stole 13 works of art worth $500 million. It was the largest art theft in history, and the museum has offered a $10 million reward for information leading to the return of the works. This mystery has fascinated art lovers for years, and despite the FBI's best efforts, it remains unsolved. Read on to find out about the stolen works and how it happened.

Do you fancy yourself as a puzzle solver? Here's your chance to try your hand at one of the internet's most difficult unsolved puzzles and join a mysterious top-secret club. Three puzzles were set, but one remains unsolved.