The Imperial Castle (Castello dell'Imperatore e Cassero)

The Imperial Castle rises above Santa Maria delle Carceri Square, located about 400 m south of Cathedral Square.

The Imperial Castle in Prato is the only example of Swabian architecture in northern central Italy. The citadel was built by the Sicilian architect Riccardo da Lentini in 1237-48 by order of Emperor Frederick II. Presumably, the death of Frederick II (1250) prevented the completion of the interior. In the plan of the fortress there is a square, at the corners of which there are powerful square at the base of the tower. There are also towers in the middle of each side of the fortress, i.e. there is another one between the two corner towers. Those towers that are located in the middle of the eastern wall and the southern wall have an original base - a pentagon. The towers at the center of the north wall and the west wall were once much higher and used as watchtowers. According to some sources, these two high towers (they preserved their height until the 18th century) are the remains of the more ancient fortress of Alberti, on the site of which the Imperial Castle was built.

The castle is built of white limestone. Its walls are crowned with Ghibellin teeth - in the form of the so-called swallow tail.