It was built in 1402 for Nicolò III d’Este by Bartolino Ploti, also the architect of Ferrara and Mantova castles (1385 and 1395, respectively).
It was surrounded by a moat on three sides, while the river provided a natural line of defence on the fourth. In 1425, Giovanni da Siena converted it into a residence for the Este family, knocking down part of the crenelated courtyards to create an exquisite three-level loggia, while the interiors were decorated with frescoes. He also built an elegant entrance by water from the east. Acquired by the city council in 1864, the castle underwent a series of major restoration and preservation works from 1896.
Until the mid 20th century, the castle housed the local gaol, but an ambitious new project began in the 1980s to return the building to public use. In parallel with the restoration work, archaeologists made a number of precious finds that are now on display inside the castle in the Civic Museums.
The structure was badly damaged by an earthquake in May 2012; access to the castle is currently forbidden for restoration.