Trani Castle is part of an imposing defensive system built by Frederick II of Swabia to protect the Kingdom of Sicily . It rises a short distance from the famous cathedral, strategically placed in the center of a bay, whose shallow waters have always been an excellent natural defense, both from the fury of the waves and from possible enemy attacks. Trani Castle was built on the model of the Crusader castles of the Holy Land, in turn debtors of the Roman castra, with a quadrangular plan, reinforced at the top by four square towers of equal height. In the 16th century, with the advent of firearms, the castle was adapted to the new defensive techniques, after which it was again the subject of adaptation works in the 19th century to adapt it to the prison function. The building has two monumental halls on the first plan, from the Frederick era. This central nucleus was enlarged with the construction of bastions , the one to the north-east with a square plan and the one to the south-west with a spearhead, connected by the rampart which encloses large secondary courtyards. The body of the casemates, built in the Renaissance period , delimits the central courtyard. A visit to the castle allows you to know, through the succession of the various rooms and courtyards, the alternation of the construction/defensive techniques that made the castle in the Middle Ages one of the most modern defensive bulwarks of the Swabian dynasty, then moving on to the Renaissance , with the thickening of the southern front and the construction of the ramparts and ending with the interventions of the nineteenth century, with the prison cells and the clock tower. In the Castle Museum , located on the ground floor of the square bastion, it houses stone and ceramic finds from the excavations carried out during the 20th century restorations.