Palazzo San Sebastiano sits just inside Mantua's southern edge, close enough to Palazzo Te that the two naturally pair together. Francesco II Gonzaga built it as a residence at the turn of the sixteenth century, and even after losses and later alterations it still carries the calm proportions of a courtly Renaissance palace.
The museum is useful because it fills in Mantua's local story beyond the headline sights. Expect sculpture, civic collections, fragments of Gonzaga imagery, and context for the city that produced Mantegna, Giulio Romano, and one of northern Italy's more theatrical courts. It is not the first stop in Mantua, but it rewards anyone staying long enough to look past the obvious palaces.