...scientists have uncovered a hidden feature underneath a medieval castle in Milan, Italy, that researchers once could only speculate about based on a sketch of Leonardo's from around 1495 and references in other historical sources — underground passageways that were likely intended for soldiers to use in the event that the castle's defenses had been breached.The discovery, which the Politecnico di Milano announced in January, came about through a series of surveys that aimed to digitize the 15th century Sforza Castle's underground structures through nondestructive methods such as ground-penetrating radar and laser scanning...Biolo and her team originally intended to digitize...