The Castle of Barletta is the architectural result of various stratifications, which are the cause of the succession of different ruling dynasties from the 11th century to the 18th century (Normans, Swabians, Angevins, Aragonese, Spanish). However, the great interest and love shown by Frederick II of Swabia for Barletta and Apulia in general led to the castle being called Swabian par excellence.

Amongst the beauty and architectural majesty of the Castle there are: the Civic Museum, the only existing bust of Frederick II (dating back to the 13th century), the Sarcophagus of the Apostles, a high stone relief (dating back to the period between the 3rd and 4th centuries) and the Municipal Library in which around 90,000 volumes are preserved and accessible to the public.