Architect Bartolino of Novara started the construction of this massive building in 1395, on the orders of Francesco Gonzaga.

The castle was a good defence bastion and a symbol of power; its position ensured to control the lakes and to give the Gonzaga family shelter in case of riots. It is a quadrangular building with 4 angle towers and 3 gates – once, each with a drawbridge. 
The castle became soon a part of the Ducal Palace itself.
During the Renaissance, Florentine architect Luca Fancelli built an elegant porch to surround the two northern sides of the castle; this became Piazza Castello.

A wide spiral staircase leads from ground floor to Sala degli Stemmi – id est the coats of arms room - and Salone degli Affreschi – id est the frescoes room -, where you may admire several Mantegna's grotesques with monsters and centaurs. From here, you may access Sala delle Sigle – id est the initials room, which was Francesco Gonzaga's and Isabella d’Este's wedding room - and Sala del Fregio – id est the frieze room, which is decked with golden feathering and volutes.

In the north eastern tower, left of Sala dei Soli – id est the suns room – there is the famous Camera Picta, also known as Camera degli Sposi – id est the bride and groom's room –, which is Mantegna's masterpiece, and which was already admired by Lucrezia Borgia and duke Alfonso D'Este. Its frescoes depict marquis Ludovico Gonzaga's family and court, and the meeting between the marquis and his son Francesco, which was a cardinal. A beautiful trompe l’oeil decks the ceiling of the room.