Although Leonardo da Vinci is best known for his art and scientific inventions, he was also involved in the design of military structures and defensive systems. A team of researchers has now uncovered a series of hidden tunnels beneath a medieval castle in Milan, which may have been depicted in one of da Vinci’s sketches from the fifteenth century.
For years, historians have debated whether a series of underground passageways at Sforza Castle, in Milan, sketched by Leonardo da Vinci, around 1495, actually existed.
The Sforza Castle connection
During the late fifteenth century, da Vinci spent significant time at the court of Duke Ludovico Sforza in Milan. During this period, he made drawings of defensive structures that closely resemble the current layout of Sforza Castle. However, as many of da Vinci’s architectural sketches were primarily theoretical exercises rather than practical blueprints, it remained uncertain whether the underground tunnels he depicted were ever constructed.
Even if the tunnels were built, another question lingered: would they have survived the passage of time? The original Sforza Castle was six times its current size, making it unclear how much of the medieval fortifications remain intact today.
New research sheds light on ancient tunnels
According to the Politecnico di Milano, new research suggests the tunnels may indeed still exist. Between 2021 and 2023, as part of the doctoral thesis of Francesca Biolo — now an architect and research fellow in the department of architecture — a series of surveys were conducted using non-invasive techniques such as ground-penetrating radar and laser scanning.
“Our findings serve as yet another reminder of how deeply embedded history is within our cities”, Biolo said in an email statement to CNN. “Only through awareness of this fact, combined with a thorough understanding of history and architecture, can we truly appreciate the importance of preserving and enhancing our cultural and architectural heritage.”
A surprising discovery beneath the Ghirlanda
The researchers focused their study on an area beneath the Ghirlanda, a protective outer wall of the castle. While the existence of one underground passageway was already known and accessible to tourists, the team made an unexpected discovery: a second tunnel.
This newly discovered tunnel runs parallel to the previously known passage, approximately a metre below the surface. According to Biolo, soldiers may have used the second tunnel to defend and reclaim the Ghirlanda against enemy forces.
Whether da Vinci played a role in its design remains uncertain, but given his architectural expertise and presence at the Sforza court, it is a strong possibility.
“It is always important to be able to reconstruct the past as precisely and as firmly as possible”, Dr. Francesca Fiorani, an art history professor and resident expert on Leonardo at the University of Virginia in Charlottesville, told CNN. “In the case of Leonardo, we know that most of his drawings, especially the architectural drawings, were ‘mental’ exercises, ideas for innovative buildings, but that they were not meant as blueprint for actual construction, just ideas of innovative building: paper architecture that existed only as drawings on paper, one might say. Whether his drawings and the tunnels recently discovered correspond (is) a matter (that) needs to be determined with further investigation.”
A tunnel leading to a Basilica?
The survey also uncovered several underground chambers and additional tunnels, one of which appears to lead towards the Basilica of Santa Maria delle Grazie — the resting place of Beatrice d’Este, the wife of Duke Ludovico Sforza, also known as Ludovico il Moro.
According to the Politecnico di Milano, historical sources suggest that the duke may have commissioned the tunnel to provide a direct route to his wife’s tomb. Further research is required to determine whether the tunnel indeed reaches the basilica.
