Once only indicated through a sketch by Leonardo da Vinci from around 1495, concealed passageways have been discovered underneath the Sforza Castle in Milan, Italy.

A mysterious network of tunnels, hidden underneath a medieval castle, sketched by Leonardo da Vinci has been finally uncovered by scientists. The discovery was made after a series of surveys that were conducted to digitise 15th-century Sforza Castle's underground structures using ground-penetrating radar and laser scanning.

Researchers in Italy may have uncovered underground tunnels beneath Milan’s Sforza Castle that were once only known through a sketch by Leonardo da Vinci, according to a report by CNN.

A team at the Polytechnic University of Milan uncovered secret tunnels beneath Sforza Castle, potentially linked to Leonardo da Vinci's designs.