Italy's Iconic Sforza Castle Was Hiding A Big Secret Revealed By Leonardo Da Vinci's Notebook

Between having the most UNESCO World Heritage Sites on Earth and multitudes of monuments, ruins, gardens, historic city centers, and villages bestowed by civilizations from the prehistoric Etruscans and Nuragic to Romans and Greeks, Italy can seem like a sprawling 117,000-square-mile open-air museum. But the recent discovery of a labyrinthine network of secret tunnels hiding beneath Sforza Castle, one of Milan's most iconic landmarks, reveals that what lies beneath the country is much more than meets the eye.

For more than half a century, rumors of these subterranean passageways have swirled but never surfaced. They initially emanated from the Codex Forster I notebook that multi-hyphenate Leonardo da Vinci kept during the late 1400s as artist-and-engineer-in-residence in Duke Ludovico Sforza's court. Within the codex's pages, the Renaissance's most illustrious genius and also its most notorious prankster drew in detail a practical annotation of how daily life intersected engineering, art, and logistics in his trademark mirror-image script — including maps of underground cavities and corridors not recorded in any accounts of the fortress, which was built in the 1300s. Given da Vinci's track record of is-it-or-isn't-it controversies, such as the enigmatic smile of the
"Mona Lisa" and the mysterious symbolism of "The Last Supper," no one could tell if this was fact or fantasy.

Until 2021, when Politecnico di Milano researcher Francesca Biolo, using these sketches as an inspirational blueprint, beamed radar and laser scans into the ground and discovered rooms and channels matching da Vinci's charts, lurking about 3 feet beneath the citadel's four turrets, three courtyards, frescoed rooms, library, and lake. Finally, Sforza Castle's deepest secret has come to light — a fascinating facet in the heart of an Italian city known for food and fashion.

These tunnels unveil a gentle soul within the magnificence of Sforza Castle, resplendent in red brick, with a majestic clock tower that tips the clouds over the Milanese skyline. While these concealed courses, bricked and topped with barrel vaults, enhanced the castle's defenses, one branch runs two-thirds of a mile towards the Basilica of Santa Maria delle Grazie (home to "The Last Supper"). Struck by grief after his wife died during childbirth in 1497, it's likely that Sforza constructed this private and seamless entry to her tomb, a poignant declaration of devotion reminiscent of Italy's legendary love stories, such as Romeo and Juliet, set in Verona, the country's most romantic city.

While these passages aren't open to the public, you can tour the Ghirlanda trench, which rings the castle under its moat and imagine how the polymath Leonardo da Vinci, also an expert on military structures, had a hand in designing these fortifications to keep enemy forces out. Marvel at his artistic legacy in the castle's Sala delle Asse for a spectacular fresco glowing with the three-dimensional effect of a painted optical illusion. These 16 mulberry trees, unfurling from walls to a ceiling canopy of entwined branches embracing the Sforza coat of arms right in the center, are both the maestro's cheeky homage to the duke's Il Moro nickname ("mulberry" in Italian) and his tactful approach to political alliances (the mulberry symbolizes prudence).

Milan is where da Vinci found fame and acclaim, 200 miles from his breathtaking birthplace in Tuscany. See how his masterpieces still vividly shape the city's cultural landscape at the Leonardo da Vinci Museum and in a rare surviving painting at the Pinacoteca, and experience his visionary inventions at his eponymous Museum of Science and Technology and the Navigli Canals.