An underground tunnel network long rumored thanks to drawings by Leonardo da Vinci under Milan’s Sforza Castle are proven to exist. Ground-penetrating radar and laser scanning revealed that the historic passages made famous by a Leonardo da Vinci drawing is just one of multiple tunnel sections.

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.

Using ground-penetrating radar and laser scanners, researchers identified subterranean structures just a few feet below the ground. The pathways may connect Sforza Castle to a nearby basilica

Italy’s famed Sforza Castle is a focal point for historians, architects, and art lovers—as well as a source of many legends. One of the most prominent rumors surrounding the over 575-year-old fortress has long been the existence of secret passageways beneath the grounds originally hinted at by Leonardo da Vinci.

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