Castello dell'Imperatore (Italian: "Emperor's Castle") is a castle in Prato, Tuscany, Italy. Located near the church of Santa Maria delle Carceri, it is the northernmost castle built for the medieval emperor and King of Sicily Frederick II.
The castle was erected by order of Frederick II starting from 1240, over a fortress of the Alberti family, of which today two towers (missing their upper sections) remain. It is one of the four major structures on which the reputation of Frederick as the builder-Emperor rests, and the only one north of the Kingdom of Naples.Its original destination was as Imperial residence, which was annexed to the second (12th century) line of walls of Prato. It was partially surrounded by a moat and was connected to the jails (carceri) from which the nearby sanctuary is named. It has eight towers, like Frederick's Castel del Monte in Apulia.
The construction was halted at the emperor's death in 1250. In the following century, under the Florentine dominion, the castle was connected to the third line of city walls by means of a covered corridor, called Corridore del Cassero.
In the 1930s, under the Fascist government of Italy, all the annexed buildings, both exterior and interior, were demolished, and the castle received the current appearance. In the rear area are the remains of a hospital and of a church of the Knights of Malta.
