
New research uncovered hidden passages under Sforza Castle, potentially confirming legends linked to Leonardo da Vinci’s designs.
As part of a PhD thesis, the Politecnico di Milano conducted an advanced technological survey in collaboration with the Sforza Castle, with technical support from Codevintec.
The investigation uncovered numerous underground passages beneath the Castle, particularly in the area once occupied by the “Ghirlanda,” or outer wall. Some of these passages may be connected to secret military routes depicted in Leonardo da Vinci’s drawings. Historical records suggest that Ludovico il Moro commissioned the construction of an underground passage to visit his beloved wife, Beatrice d’Este, who was buried in the Basilica of Santa Maria delle Grazie.

This passageway is immortalized in Leonardo’s drawings, and has long been the subject of legends and considerable speculation. But now, thanks to technology, it seems that its existence can be confirmed. However, there are many other secret passageways.
Advanced Technologies Unveil Hidden Structures
The investigation used advanced technologies, such as GPR and laser scanners, to create an accurate map of the Castle’s sub-surface and the underground structures. These instruments were able to reveal underground cavities and passageways about a foot or two beneath the surface.
As Franco Guzzetti, professor of Geomatics at the Politecnico di Milano, explained: “The aim is to create a digital twin of the Sforza Castle, a digital model that not only shows the current appearance of the Castle, but also allows us to explore the past, by revealing ancient structures that are no longer visible.”

As well as providing a historical record, the data collected could be integrated with augmented reality to develop immersive experience projects that combine history and innovation.
Francesca Biolo, a researcher at the ABC Department of the Politecnico, also pointed out: “The GDR technology has added to our 3D model by providing data about well-known but inaccessible spaces, revealing unknown pathways and suggesting ideas for further research into these secret passages.”
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