Looking for Leonardo Part 3

In a remarkable blend of history, engineering, and modern archaeology, a series of secret underground passages have been discovered beneath Milan’s Sforza Castle (Castello Sforzesco)—and they may have been designed by none other than Leonardo da Vinci.

This groundbreaking find, made possible through the study of centuries-old sketches attributed to the Renaissance genius, reveals a hidden layer of Milan’s past, offering fresh insight into the city’s strategic architecture during the 15th century.

A Renaissance Mastermind Behind Milan’s Defenses?

For centuries, Milan’s Castello Sforzesco has stood as a symbol of power, resilience, and artistic grandeur. Originally built as a medieval fortress, it was later transformed by the Sforza dynasty into a center for military strategy and artistic patronage. During his time in Milan, Leonardo da Vinci—who was employed at the Sforza court—was tasked with fortification projects, applying his brilliant mind to the defense of the city.

His sketches, preserved in historical archives, long hinted at the existence of hidden passageways and underground structures beneath the castle. Until now, however, they had remained a tantalizing mystery.

The Discovery: Archaeology Meets Innovation

A team of archaeologists, engineers, and historians recently set out to verify the accuracy of da Vinci’s drawings recorded in the Codex Forster I.

Using ground-penetrating radar and advanced scanning technology, they were able to locate what appeared to be sealed tunnels and hidden rooms beneath the castle’s foundation.

The team—made up of experts from Polytechnic University of Milan, Codevintec, and Sforza Castel employed a ground-penetrating radar and laser scanning that mapped multiple feet under the castle. With the help of virtual reality, researchers are able to recreate the spaces.

“The goal is to create a digital twin of the Sforza Castle, a digital model that not only represents the current appearances of the castle but also allows you to explore the past, recovering historical elements that are no longer visible,” Franco Guzzetti, professor of geomatics at Polytechnic University of Milan, said in a statement.

Upon excavation, the team uncovered a network of subterranean corridors, likely constructed to allow for discreet movement of troops, emergency escapes, and secret supply routes—a military strategy well ahead of its time. The craftsmanship of the tunnels, along with their calculated angles and air circulation features, aligns with Leonardo’s visionary approach to engineering.

Milan’s Living History: What This Means for the City

This discovery redefines what we know about Milan’s architectural and military ingenuity during the Renaissance. It also highlights Leonardo da Vinci’s impact beyond his well-known artistic masterpieces. His involvement in civil and military engineering projects demonstrates how deeply intertwined art, science, and strategy were in Renaissance Milan.

Moreover, the find raises the possibility that other hidden passageways or secret chambers may still lie beneath Milan’s historic landmarks, waiting to be revealed.

With ongoing archaeological efforts, this newly uncovered underground world may soon become accessible to the public, further enriching the city’s cultural tourism and historical narrative.

Milan: A City That Never Stops Revealing Its Secrets

For travelers and history lovers, this is another reminder that Milan is far more than fashion and finance—it is a city where the past continually interacts with the present. Walking through Castello Sforzesco, visitors may soon be able to descend into these long-lost tunnels, stepping into the very spaces where Renaissance-era Milanese soldiers once navigated in secrecy.

As research continues, one can only wonder: What other Renaissance secrets might Milan still be hiding beneath its streets?

Learn more:

1. Secret Underground Passages Described in Leonardo da Vinci's Sketches Discovered Beneath Milan's Sforza Castle. La Brújula Verde, January 2025.

2. The Engineering Mind of Leonardo da Vinci and His Architectural Contributions to Milan. Shelidon, N.10.2023.

3. Milan’s Underground: New Archaeological Finds on the M4 Metro Project. Wanted in Milan, June 2018.

4. Historical Urban Planning and Fortifications in Milan. The Art Newspaper, February 2022.