The Sforza Castle (Italian: Castello Sforzesco [kasˈtɛllo sforˈtsesko]; Milanese: Castell Sforzesch [kasˈtɛl sfurˈsɛsk]) is a medieval fortification located in Milan, northern Italy.

In the following years, however, the castle was damaged by assaults from Italian, French and German troops; a bastion, known as tenaglia, was added, perhaps designed by Cesare Cesariano.

[5][6] After the French victory in the Battle of Marignano in 1515, the defeated Maximilian Sforza, his Swiss mercenaries, as well as the cardinal-bishop of Sion retreated into the castle.

When Francesco II Sforza returned briefly to power in Milan, he had the fortress restored and enlarged, in addition to a part of it adapted as a residence for his wife, Christina of Denmark.

[2] In 1550 works began to adapt the castle to modern fortification style, as a hexagonal (originally pentagonal) star fort, following the addition of 12 bastions.

The semi-circular Piazza Castello was constructed around the city side of the castle, surrounded by a radial street layout of new urban blocks bounded by the Foro Buonaparte.

Between 1900 and 1905 the Torre del Filarete was rebuilt, based on 16th-century drawings, as a monument to King Umberto I. Allied bombardment of Milan in 1943 during World War II severely damaged the castle.

This ghirlanda refers to a wall, protected by a ditch filled with water, built under Francesco Sforza, of which few traces remain today, including the Porta del Soccorso.

The Porta della Ghirlanda gate was entered through a ravelin (now lost) and had two entrances accessed through runways, which led to an underground passage which continued along the walls.

The external side which once faced the walled city has two round towers, commissioned by Francesco Sforza to replace the former square ones, which had become less suitable to defend against fire weapons.

[11][12] The Biblioteca Trivulziana is a library of the Municipality of Milan located inside the Sforza Castle, annexed to the Civic Historical Archive.