The Crown of Spain acquired, as it is known, the kingdom of Naples in 1504, which as Viceregno it will be part of the Spanish empire for more than two centuries. The empire between the sixteenth and seventeenth centuries was faced with various challenges, both internal and boundary, particularly maritime, attacked by the Ottoman expansion. Urban and coastal fortification plans were prepared and put in place to defend the territory. Calabria was also a participant in this effort, which the Viceroys directed and followed from Naples, with the approval of Madrid. This study examines the projects and achievements implemented in the chronological period under consideration in Calabria Ultra, current provinces of Reggio Calabria, Vibo Valentia, Catanzaro and Crotone. Particular attention is paid to coastal defense plans with the design of new towers, which combined with city walls and/or castles in state-owned or feudal cities, complement the defensive projects of the coasts. It is important to highlight how the types adopted are consistent with coherent implementations implemented in the extended territory of the empire, thus declaring widespread knowledge and cultural identity in the Europe of the time.