Apulia region is dotted by a complex system of fortress, due to its geographical position, the size of its coasts and its peculiar story. From 1223, Frederick II the Swabian began a project to restore the already existing fortress and to build new ones. Although this project aimed mainly at defending the surrounding area, it had deep influence on the Apulian economy, population and landscape. Apulia possesses the highest number of ancient Swabian castles: 69 "castra" and 42 "domus" are to be found here. 

The most famous is Castel del Monte, that was built around 1240 for Frederick II; it's known both for the recurrent use of the number eight (external perimeter of the courtyard, shape and number of towers) which is full of symbolic meaning and because of its uncertain destination. UNESCO included it in the World Heritage in 1996 because of its uniqueness.
The sixteen trapeizoidal rooms are characterised by refined sculptural adornments in which ancient and modern are blended along with elements from Arab world.
In 1876 it was purchased by the Italian State in a very precarious condition but lenghty restoration work has enabled its recovery.

Bari Castle - which was historically attributed to Ruggero The Norman - dates back to 1131; it was built on an already existing building dating back to Byzantine period. When Bari was destroyed by William the Wicked in 1156, also the castle, founded by the Normans themselves, suffered heavy damages. Between 1233 and 1240 it was restored by Frederick II of Swabia, who enhanced its residential and decorative aspects, for instance through the realization of a monumental portal and a portico alongside the perimeter of the inner courtyard.

Later on the 16th century, under Isabel of Aragon and her daughter Bona Sforza, the rampart wall was built and the central courtyard repaired with the two ramp steps. In the 19th century the castle was used as a prison and later as an army barracks. It currently holds an interesting Gallery of Plaster Casts with more than 200 reproductions of Apulian monumental sculptures from the 11th to the 16th century; it is also the venue of exhibition at an international level.