Castel Capuano, which was built by the Norman king William I, known as the Malo to distinguish it from his son William II, known as the Good. It was so called because it is located at the end of the decumanus major, near Porta Capuana (from here began the road to Capua). William I had it built on the ruins of an ancient ducal building, while in Greco-Roman times there stood an imposing public building, the Baths or the Gymnasium. The castle housed the nobles until the Spanish viceroy don Pedro de Toledo, the same one who built the Spanish Quarters in the 16th century, gathered all the city’s courts of justice there and turned it into a courthouse with prisons. Famous is the Fountain of Formiello, built in 1490 as a drinking trough for horses, the "Salone dei Busti", where the busts of the major Neapolitan jurists are displayed.
