Sforza Castle Sforza Castle ( Italian : " Castello Sforzesco " ) is a castle in Milan , northern Italy . It was built in the 15th century by Francesco Sforza , Duke of Milan , on the remains of a 14th - century fortification . Later renovated and enlarged , in the 16th and 17th centuries it was one of the largest citadels in Europe . Largely remade by Luca Beltrami in 1891 - 1905 , it now houses several of the city ' s museums and art collections . History . The original construction was ordered by local lord Galeazzo II Visconti in 1358 - c . 1370 ; this castle was known as " Castello di Porta Giova " ( or " Porta Zubia " ) , from the name of a gate in walls located nearby . His successors Gian Galeazzo , Giovanni Maria and Filippo Maria Visconti enlarged it , until it became a square - plan castle with 200 m - long sides , four towers at the corners and up to 7 m - thick walls . The castle was the main residence in the city of its Visconti lords , and was destroyed by the short - lived Golden Ambrosian Republic which ousted them in 1447 . In 1450 , Francesco Sforza , once shattered the republicans , began reconstruction of the castle to turn it into his princely residence . In 1452 he hired sculptor and architect Filarete to design and decorate the central tower , which is indeed still known as " Torre del Filarete " . After Francesco ' s death , the construction was continued by his son Galeazzo Maria , under architect Benedetto Ferrini . The decoration was executed by local painters . In 1476 , during the regency of Bona of Savoy , the tower with her name was built . In 1494 Ludovico Sforza became lord of Milan , and called numerous artists to decorate the castle . These include Leonardo da Vinci ( who frescoed several rooms , in collaboration with Bernardino Zenale and Bernardino Butinone ) and Bramante , who painted frescoes in the " Sala del Tesoro " ; the " Sala della Balla " was decorated with Francesco Sforza ' s deeds . Around 1498 , Leonardo worked at the ceiling of the " Sala delle Asse " , painting decorations of vegetable motifs . 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 . After the French victory in the 1515 Battle of Marignano , the defeated Maximilian Sforza , his Swiss mercenaries , and the cardinal - bishop of Sion retreated into the castle . However , King Francis I of France followed them into Milan , and his sapper s placed mines under the castle ' s foundations , whereupon the defenders capitulated . In 1521 , in a period in which was used as weapons depot , the Torre del Filarete exploded . When Francesco II Sforza returned briefly into power in Milan , he had the fortress restored and enlarged , and a part of it adapted as residence for his wife , Christina of Denmark . Under the Spanish domination which followed , the castle became a citadel , as the governor ' s seat was moved to the Ducal Palace ( 1535 ) . Its garrison varied from 1000 to 3000 men , led by a Spanish castellan . In 1550 works began to adapt the castle to modern fortification style , as an hexagon ( originally pentagon ) - shaped star fort , following the addition of 12 bastions . The external fortifications reached 3 km in length and covered an area of 25 . 9 hectares . The castle remained in use as a fort also after the Spaniards were replaced by the Austrians in Lombardy . Most of the outer fortifications were demolished during the period of Napoleonic rule in Milan under the Cisalpine Republic . 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 Buonoparte . The area on the " country " side of the castle was laid out as a vast 700m by 700m square parade ground known as Piazza d ' Armi . After the unification of Italy in the 19th century , the castle was transferred from military use to the city of Milan . Parco Sempione , one of the largest parks in the city , was created on the former parade grounds . The government of Milan undertook restoration works , directed by Luca Beltrami . The Via Dante was cut through the medieval street layout in the 1880s to provide a direct promenade between the castle and the Duomo on axis with the main gate . The central torre Filarete above the main city entrance was rebuilt , basing on 16th century drawings , between 1900 and 1905 as a monument to King Umberto I . Allied bombardment of Milan in 1943 during World War II severely damaged the castle . The post - war reconstruction of the building for museum purposes was undertaken by the BBPR architectural partnership . Description . The castle has a quadrangular plan , site across the city ' s walls . The wall which once faced the countryside north to Milan has square towers and has 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 " : both received wide windows during the Sforza age . 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 ) and the " Cortile della Ghirlanda " . This " ghirlanda " refers to a wall , protected by a ditch filled by water , built under Francesco Sforza , of which few traces remain today , including the " Porta del Soccorso " . Remains of two later ravelin s can be seen in correspondence of the point in which the castle was joined by the city walls ( near the " Porta Comasina " gate ) and the " Porta del Carmine " . The " Porta della Ghirlanda " gate was entered through a ravelin ( now lost ) and had two entrances accessed through runways , on which lead 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 . The central tower , called " Torre del Filarete " , is a modern reconstruction . The round towers lost the upper parts under the Austrians , which needed open space for their artillery . Their upper sector existing today is also a modern restoration . The " Torre del Filarete " and the " Porta del Santo Spirito " , located more southwards , are both preceded by a ravelin . The main gate leads to a large court from which several internal features can be seen . These include the Tower of Bonza of Savoy ( 1476 ) and the " Rocchetta " , a sort of internal defensive ridotto with a ate of its own . At the right of the " Porta del Carmine " are remains of two 15th century courts . The " Rocchetta " , whose access gate from the main court ( a modern addition ) features the coat of arms of the Sforza , has an internal courts with , on three sides , a portico with 15th century arcades . The " Corte Ducale " is the wing of the castle originally used as ducal residence ; it features a court with two loggia s , a smaller one at left and a larger one at its end , called " Loggiato dell ' Elefante " due to the presence of a fresco of an elephant . The Civic Museums . The Castello complex includes some museums : The Trivulziana Library holds Leonardo da Vinci ' s ' Codex Trivulzianus ' manuscript . Also in 2012 new paintings attributable to Michelangelo Merisi da Caravaggio have been discovered at the castle .