The Ducal Palace was the main residence of the Gonzaga family, lords, marquises and finally dukes of the city of Mantua. It took the name of Royal Palace during the Austrian domination starting from the time of Maria Theresa of Austria.
Distinct and separate rooms were built in different periods starting from the 13th century, initially by the Bonacolsi family and later at the instigation of the Gonzaga. It was Duke Guglielmo who commissioned the prefect of the Factories Giovan Battista Bertani to connect the various buildings in an organic form so as to create, starting from 1556, a single grandiose monumental and architectural complex, one of the largest in Europe (approximately 34,000 m²), which extended between the shore of the Lower Lake and Piazza Sordello, the ancient Piazza di San Pietro. After Bertani's death in 1576, the work was continued by Bernardino Facciotto who completed the integration of gardens, squares, loggias, galleries, exedras and courtyards, definitively establishing the appearance of the ducal residence. The interior of the palace is almost bare because once impoverished, the Gonzagas had to sell works of art (especially to Charles I of England) and furnishings, some of which were later stolen by Napoleon.
The Palazzo del Capitano overlooking Piazza Sordello is the oldest building of the Ducal Palace commissioned by Guido Bonacolsi at the end of the thirteenth century. Initially built on two floors and separated from the Magna Domus by an alley, in the early 1300s it was raised by one floor and joined to the Magna Domus itself by the monumental façade with portico, which has essentially remained the same to this day. The second added floor consists of a single enormous hall (67 x 15 metres) called Dell'Armeria, also known as the Salone della Dieta, as it hosted the Diet of Mantua in 1459.