Commissioned in the 13th Century by Viscount Galeazzo II in Milan, Italy – Sforza Castle was at one time one of the largest Citadels in Europe. Extensively renovated in the 16th and 17th Centuries, it's walls are 10 feet thick. Of the Quadrangular building design, it once featured both dry and wet Ditch/Moat systems. It also featured an unusual underground access tunnel which lead to the Castles entrances. Originally featuring 6 Round Defensive Towers (with 2 to the front and 2 to the rear), these were designed to support cannon (which also protected the nearby Town). A large Inner Bailey lead to a central (but somewhat smaller) Donjon.
The Castle's garrison could hold up to 3,000 troops. It featured an Armory and weapons production facilities. After The Battle of Marignano in 1515, Milanese troops retreated to Soforza. The French enemy deployed Sappers (anti-fortification specialists), to undermine the Castle. The garrison surrendered before the fortification could be destroyed. The current Castle houses 8 historical Museums and 1 Library. It can be visited by the Public.