At present, the Castle is a quadrilateral enclosing the PIAZZA DELLE ARMI, with its central tower facing the city designed by Filarete and later restored by Luca Beltrami and two cylindrical towers covered with bosses on each side (the TORRIONE DEI CARMINI and TORRIONE DI SANTO SPIRITO). At the beginning of the 20th century, some new buildings, which now house offices, were added to the walls facing south and west. The TORRE DI BONA DI SAVOIA is built on one side of the Rocchetta, just near the place where there was the old PORTA GIOVIA, one of the medieval gates providing access to the city. The FOSSATO MORTO (dead moat), which can be seen today around the inner walls of the castle, was the original moat around the medieval town walls.

The other part of the quadrilateral is covered by the ROCCHETTA and the DUCAL COURTYARD. The Rocchetta is the most protected area. Situated in the northwestern part of the castle, it is provided with high windowless walls, an inner courtyard and a square tower facing the surrounding countryside named TORRE CASTELLANA. On the ground floor of this tower is the SALA DEL TESORO (Treasury room), which contains the beautiful frescos painted by Bramantino. The Ducal Courtyard encloses the TORRE FALCONIERA. On the ground floor of the tower is the Sala delle Asse decorated with paintings by Leonardo da Vinci. On the first floor is the Sala XX, which was the bedroom of duchess Isabella d'Aragona, Gian Galeazzo Sforza's wife.

The U-shaped Ducal Courtyard encloses a pretty garden. On the short side is the PORTICO DELL'ELEFANTE, named after a fresco that is painted on the arcade. An elegant ramp of stairs leads to the LOGGETTA DI GALEAZZO MARIA, the ducal loggia on the first floor. The moat enclosing the above-mentioned quadrilateral was in its turn surrounded by another circle of defensive walls built during the Renaissance period with the aim of protecting both the walls to the east and west and the façade on the back facing the Sforza family's garden, the so-called BARCO. This second circle of walls was called GHIRLANDA. Provided with three circular towers and connected to the inner space by means of the RIVELLINI, (RIVELLINO DI SANTO SPIRITO, RIVELLINO DEI CARMINI), the Ghirlanda was destined for defensive purposes in case of attacks coming from the countryside.

The Museum of Ancient Art contains works ranging from the early Christian age to the sixteenth century, and environments such as the Hall of the Banner, decorated the Ducal Chapel and the Sala delle Asse painted by Leonardo da Vinci and also the Pietà Rondanini by Michelangelo

The collection of the cabinet documents very well the history of the Lombard furniture , with some rather large openings on Roman Baroque and Genoese and Venetian eighteenth century.

The civic picture gallery offers a course on the history of Lombard painting, sprayed by the contributions of other cultural areas, especially the Venetian school, and flanked by the presence of the great masters of Italian art.

The Collections of Applied Arts are an important part of the Civic Museums of Castello Sforzesco: of many collections extremely varied by type, with a period of time ranging from the Middle Ages to the twentieth century, such as furniture, tapestries, textiles, ceramics, glass, jewelry, sculptures wood and ivory, bronze and wrought ironwork, weapons, leathers, scientific instruments, for a set of the most important in the world for quality and quantity.
The Civic Museum of Musical Instruments is one of the largest in Europe and second Italy for importance and number of findings (over 900 of which about 500 exposed) ranging from the sixteenth century to the second half of the twentieth century.
The collections of prehistoric objects mainly from northern show in a rich way and with little gaps the area's history over the last 5000 years before Christ.
The exposure of the Egyptian Collection of the Civic Archaeological Museum offers the public a selection of about 250 of the more than 2500 pieces that make up the whole collection.
In the fifteenth century the quadrilateral inside the castle was surrounded by a moat, defended by a second round of walls called garland - demolished in 1893 - having three round towers
The garland was connected to the Castle by three ravelins - foreparts with defense functions - themselves communicating with the medieval walls of the city, and was covered on the inside by a gallery (covered road or street secret), which is perfectly preserved.