Castle Sforzesco was built in the 15th century by Francesco Sforza. It is built on a site of an older fortress, built earlier by Galeanzzo Visconti. Visconted used the fortress more as a personal protection from his brother Bernabo, who he used to share the rule of Milan with, rather than for protection of the city. In the following years his successors enriched and enlarged the castle by adding towers and strengthening the walls. Despite these efforts however the castle is destroyed in 1477 by the Ambrosian Republic that existed for a while. The Ambrosian Republic put Francesco Sforza in charge with the command of the troops against Venice.
Francesco Sforza was married to the only daughter of the last male heir of House Visconti – Maria. Although he had a deal the republicans, Sforza made one with the Venetians as well and at the end victoriously returned to Milan, as a duke. He turned the castle Sforzesco into his residence and quickly restored it. On his order the huge central tower known as Filarete was built. One of his successors Ludovico Srofza engaged two of the greatest artists of that time – Leonardo da Vinci and Donato Bramante. In 1499 Ludovico was forced to leave Milan and to retreat because of the troops of the French king Luis XII. In the following years the castle often changed its owners – French, Spanish, Austrian, becoming an object of vandalism. It also lost its famous central tower which was destroyed as a result of a lightning.. At that time the tower was used as a armory storage. The last of House Sforza – Francesco II tried to restore the past glory of the castle, but the splendor which he achieved did not last for long and after his death the castle lost its significance.
After the unification of Italy, Sforzesco was in such a poor condition that the city authorities intended to demolish it. It was saved by the architect Luca Beltrami, who wanted to restore it and to form halls where cultural institutions could be housed. He restored the towers Boa and Roccetta but Filarete was never built again. In 1905 the castle was opened to public. Today it houses museums and galleries as well as the city library.
You can find information on tickets and opening times here.