A fortress within the fortress, the Rocchetta was, for a brief period, the refuge of Bona di Savoia, who commissioned the construction of the high tower, before Ludovico il Moro assumed power. The bunker-like appearance of the exterior, with its high and windowless walls is rendered lighter and more appealing by the addition of three portico wings in which, in line with the wishes of Galeazzo Maria Sforza, the capitals of the columns are adorned with the coats of arms of the Visconti and Sforza families. On the side facing the the Ducal Courtyard, the coats of arms that have the addition of a half moon, the symbol of the Spanish castle governor Alvaro de Luna, indicate areas dating to the 1500s. The restorations that took place between 2010 and 2013 brought to light the Sforza motif decorations wanted by Luca Beltrami in the early 1900s.