The Castello Sforzesco was built in the 15th century by Francesco Sforza, Duke of Milan, on the remnants of a 14th-century fortification. Later renovated and enlarged, in the 16th and 17th centuries it was one of the largest citadels in Europe. Extensively rebuilt in 1891–1905, it now houses several of the city's museums and art collections and is now one of the biggest castles in Europe and one of the main landmarks in the city.
It is square in shape, with 4 towers at the corners that allowed for an easy exit route out of the city in case people had to escape from enemies. It was an efficient defensive wall, as well. The wall, which once faced the countryside north of Milan, has square towers and an ogival gate. This was once accessed through a drawbridge. The northern tower is known as Torre della Corte, while the western one is called Torre del Tesoro
The corner defended by the Torre Ducale is characterized by a loggia bridge, attributed to Bramante, and commissioned by Ludovico Sforza in the late 15th century to connect the Corte Ducale (the court in the area used as ducal residence) to the Cortile della Ghirlanda. This ghirlanda refers to a wall, protected by a ditch filled by water of which few traces remain today, which included the Porta del Soccorso.
Later, while under Austrian domination, the Sforza Castle was turned into military barracks, and neglect and decline prevailed. That is why during the unification of Italy it was decided to demolish it. In 1895 the entire building was purchased by the Comune di Milano (Municipality of Milan), which carried out a long and complicated restoration process, but in the end the castle regained its original splendour.
In 1943 it was severely damaged after bombing, but a new renovation after World War II transformed it into the citadel of museums of Milan, a place of history and memory for the entire city.