Over the centuries, the castle has been a defence fortress, a residence, military barracks and the site of museums and cultural institutions; the transformations of one of the most representative and popular monuments of Milan have been various and complex.
The defensive nature of this conspicuous structure made it a target for many sieges, demolitions and successive reconstructions of some parts during the French, Spanish and Austrian domination.
The events of the castle unfold in the city’s wide window of history, beginning with the original nucleus of the castle, named Porta Giovia, that dated back to 1358-1368 in the times of Galeazzo II Visconti. He used the castle as his residence during his stays in Milan, but above all, he used it as a military garrison.
Filippo Maria Visconti made it his fixed residence, continuing with the consolidation and construction of a real fortalice. It was Francesco Sforza who, after becoming ruler of Milan in 1450, gave particular impetus to the reconstruction of the building that was gravely damaged between 1447 and 1450.
Today the castle is home to the Civic Museums and since 1896 it has hosted one of the vastest artistic collections in the city. Inside, the Museo d’Arte Antica (Museum of Ancient Art) is custodian to the last masterpiece of Michelangelo, the Pietà Rondanini. It also hosts the Pinacoteca (Picture Gallery), Raccolta di Mobili (Furniture Collection), with pieces from the 15th to the 19th century; the Rocchetta, where one can admire the Museo delle Arti Decorative (Museum of Decorative Arts), with its extremely vast collection of ceramics; the Oreficerie (Goldsmiths); one of the largest collection of musical instruments in Europe; the Arazzi Trivulzio (Trivulzio Tapestries); the Armeria (Armoury); the Museo della Preistoria e Protostoria (the Museum of Prehistory and Protohistory); the Museo Egizio (Egyptian Museum) and the Sale Viscontee, exhibition rooms with periodic displays. Finally, many important archives and libraries are located in the castle: Biblioteca d’Arte (Library of Art), the Archivio Storico (Historic Archive), the Biblioteca Trivulziana (Trivulziana Library), the Biblioteca Archeologica e Numismatica (Archaeological and Numismatics Library), C.A.S.V.A. (Centre for Advanced Study in the Visual Arts), Raccolta delle Stampe “Achille Bertarelli” (“Achille Bertarelli” Print Collection), Archivio Fotografico (Photographic Archive) and the Raccolta Vinciana (Vinciana Collection).
In 1521, the central tower of the castle, where a munitions deposit was held, collapsed due to an accidental gun powder explosion, possibly caused by a lightning strike.
In the last 20 years of the 19th century, many proposals were put forward suggesting the demolition of the whole, or at least a good part, of the castle. Fortunately, these were not taken up and the project for the restructuring of the building was entrusted to architect Luca Beltrami, already a stout defender of the Sforza bulwark.
In 1893, the architect devised a reconstruction plan based on archive documents, paintings and contemporary literary texts that directed him towards a philological reconstruction. It provided for the recovery of decorations that were used during the era of the Sforzas, the covering of the parapet walks, the repositioning of the coat of arms of the rulers of Milan and naturally, the rebuilding of the Torre del Filarete (Filarete Tower) or the Torre Umberto I (Tower of Umberto I).
The Torre del Filarete was completely reconstructed by architect Luca Beltrami based on some graffito found in the Cascina Pozzobonelli (Pozzobonelli Farmhouse) and in an abbey. On the other hand, the architect redesigned the windows and the façade of the castle from scratch, inspired by the style of interior. The Torre del Filarete was inaugurated on the 24th September 1904 and was subsequently dedicated to Umberto I.
The antique Visconti park was reduced in size over the centuries, leaving only a dusty piazza called Piazza d’Armi, which was utilized for military exercises. Between 1891 and 1894 it was given new life thanks to the commitment of the municipal administration at the time. It cost 1, 700, 000 lira of the day for 21 hectares of green space, designed by the architect Emilio Alemagna. It is now Parco Sempione (Sempione Park).