Da Vinci’s drawings lead to discovery of secret tunnels beneath Italian Sforza Castle

Popular Mechanics reveals in its recent article that Leonardo da Vinci’s works have always been a source of wonder and discovery, from the iconic "Mona Lisa" to his intricate scientific sketches. 

Despite the depth of study and admiration his works have received over the centuries, new discoveries still emerge. Recently, researchers uncovered one such surprise: a drawing of a castle tunnel from the 1400s. 

This drawing depicted Sforza Castle and its hidden underground tunnels—tunnels that had never been located before. The team, made up of experts from Polytechnic University of Milan, Codevintec, and Sforza Castle, utilized ground-penetrating radar and laser scanning to map several feet beneath the castle’s surface. Their findings not only confirmed the existence of the tunnels referenced in da Vinci's drawings but also suggested they might be part of a larger, complex network running beneath the castle.

“The ground-penetrating radar enriched the 3D model with data on known, but inaccessible, spaces, bringing to light unknown walkways and ideas for further studies on secret passages,” Francesca Biolo, researcher at Polytechnic University of Milan, said in a statement.

The Sforza Castle gained prominence in the 1400s when Duke Francesco Sforza of Milan reconstructed an ancient site and transformed it into a grand fortress, complete with towers, courtyards, and fresco-lined halls. In 1494, his successor, Ludovico Sforza, expanded the castle’s legacy by hiring Leonardo da Vinci to create artwork for the site. As noted by Art Net, while working on this project, da Vinci documented the castle's hidden tunnel system, a discovery later recorded in the Codex Forster I.

Experts believe the tunnels were likely used for military purposes, although some parts of the system may have also had more personal functions. For example, one passageway links the castle to the Basilica of Santa Maria delle Grazie, a church commissioned by Francesco that houses da Vinci's iconic "The Last Supper." The church is also the burial site for the Sforza family, and this connection may have given castle residents quicker access to the tombs of their loved ones, such as Ludovico's wife, Beatrice d'Este.

Today, the castle complex hosts three museums: the Pinacoteca del Castello Sforzesco, the Museum of the Rondanini Pietà, and the Museum of Ancient Art.

Although the underground system may not be fully accessible at the moment, the use of ground-penetrating radar and laser scanning to confirm its existence could provide a new perspective on the Sforza Castle's hidden world.

“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,” said Franco Guzzetti, professor of geomatics at Polytechnic University of Milan, in a statement.

Incorporating augmented reality into these virtual paths could offer visitors a new way to explore the castle's underground spaces and otherwise inaccessible historical areas, creating an innovative museum experience. Da Vinci's artwork continues to captivate modern audiences once more.

By Naila Huseynova