The Imperial Door was built in 1579, at the end of the second stage of reconstruction of the medieval walls. It was dedicated to Emperor Rodolfo II of Asburgo, as one can read in the epigraph placed above the main entrance. The façade –fully covered with white marble ashlar –is interrupted in the lower part by three arched openings. Above the central opening, which features in his key brick a grotesque mask similar to the inventions of artist Giulio Romano, is placed an epigraph reciting:
“Vespasiano, by the grace of God Duke of Sabbioneta, ordered the construction of this door adorned by the Emperor’s name in 1579”
The Ducal coat of arms –lacking the Golden Fleece Chain, which Vespasiano obtained only in 1585 – is placed above the epigraph. .
The ancient upper lodge, very similar to the one seen on the Gate of Victory, was replaced in the first half of the 19th century with the present cuspidate tympanum, probably following a project by Carlo Visioli. The door is quadrangular-shaped, as well as the Door of Victory.

(Translation Ottavia Mapelli)