The castle takes up a large space in the centre of Milan, in front of the Cathedral Square (Piazza del Duomo), at the opposite side of the avenue which joins them. It was the main residence of the Dukes of Milan, built starting from 1360 by Galeazzo II Visconti and by his successors Gian Galeazzo Visconti and Francesco Maria Visconti. It was pulled down by Milan citizens in 1447 during the brief Republic period; rebuilt in 1450 by Francesco Sforza, husband of the last heir of Visconti family. To its original front were then added the entrance tower planned by Filarete and the round towers in the corners. With Ludovico Sforza called Il Moro, the castle was enriched with the works by Bramante, who planned the elegant side wind of Ponticella, and by Leonardo Da Vinci, who directed the frescoes works in the Hall of the Axes (Sala delle Asse).

During the following rules by the French, the Spaniards, the Austrians up to Napoleon Age, the castle, demoted to a military post and maken heavy with exterior wall fortifications, was seriously damaged. After the unification of Italy were planned the reconstruction works, which began with the definitive demolition of external fortifications and culminated with the complete rebuilding of the Filarete's tower, looking at the Cathedral.

Today the castle hosts some civic museums. At the ground floor there is the Museum of Ancient Art, whose exhibition is set up inside a bare environment, but for this being very evocative, since it gives the whole scene to the exhibited works. It shows mainly Lombard sculpture belonging to the Romanic, Gothic and Renaissance ages. Among the present statues, the most famous is certainly the Pietà Rondanini by Michelangelo, emblematic work essential to understand the artistic landing place by the greates sculptor of all times.

At the first floor there is the Picture Gallery, showing interesting Renaissance and Baroque paintings, with worls by Giovanni Bellini, Mantegna, Borgognone, Moroni, Tiepolo, Lorenzo Lotto, Guard́. In the basements there is instead the Archaeological Museum, with remains selected among the large collections by the National Archaeological Museum in Corso Magenta. Finally the Museum of Music Instruments, showing a large collection of instruments of all types: strings, boards, winds.