The castle in Milan that Leonardo helped redesign as a military fortress was Sforza Castle. Known in Italian as Castello Sforzesco, it stands at the heart of Milan and became closely associated with the Sforza dynasty.
The complex began as a Visconti fortress in the fourteenth century. Francesco Sforza rebuilt and enlarged it after becoming Duke of Milan in 1450, while later rulers developed it as both a fortified stronghold and a ducal residence. Leonardo worked in Milan for Ludovico Sforza, known as Il Moro, from about 1482 and contributed to military-engineering projects as well as court decoration.
Leonardo is especially associated with the castle’s Sala delle Asse, a large decorative room painted with an elaborate canopy of branches and foliage. That artistic connection can cause confusion: the castle was not designed entirely by Leonardo, nor was every defensive feature his work. Its walls, towers, moats, and later fortifications reflect several centuries of construction and alteration.