The Castle Estense or Castle of Saint Michele (Italian Castello Estense) is an imposing, moated, medieval structure in the center of Ferrara. It is a large block with four corner towers. The Guelf family of Este had dominated Ferrara by 1264, but after a bloody rebellion in 1385, Niccolò II d'Este, for his safety, erected this castle-fortress. The towers were merlated with few windows but later radically modified, adding the Loggia of Oranges, and replacing the merlons with marble balconies. Inside there is quattrocentesque courtyard. There are various rooms decorated with frescoes of Bastianino. One of the more interesting rooms of the building is the private chapel of the protestant Renée of France, wife of duke Ercole II; also famous are the dungeons where she, spouse of Niccolò III d'Este had a tragic ending. With the end of the Este Family in 1597, the castle's fabulous art collection was dispersed.
Under Ercole II, the son of Alfonso I and Lucrezia Borgia, chief artists involved were Tommaso da Carpi, Battista Dossi, Tommaso da Treviso, il Garofalo, Camillo Filippi and Girolamo da Carpi.