There's a hidden drawing underneath the "Mona Lisa" — and it shows that this masterpiece almost looked very different.

Archaeologists Blown Away After Finding Secret Tunnels That Da Vinci Had Drawn Over 500 Years Ago Researchers from the Polytechnic Institute of Milan visited the site of Italy’s famed Sforza Castle as part of a doctoral thesis and conducted a technological study.

For centuries, whispers of hidden tunnels beneath Milan’s iconic Sforza Castle have intrigued historians and treasure hunters alike.