The area of the medieval Tersana (darsena or shipyard) expanded during 13th century at the time when military victories and the flowering of overseas commerce made it necessary for the city to find a suitable site for naval purposes.Military defeats in the following century and a crisis in mercantile activities caused this area to be reconverted at the end of the 1300s, when Iacopo d’Appiano transformed it into a fortress; he built the S. Agnese tower by strengthening a previous one and created the first battlements in brickwork on the walls.