Urban walls and castles within bastioned fortifications: a contrastive analysis

This paper investigates the relationship between urban fortified walls and castles within the framework of bastioned fortifications, focusing on the transitional period from the sixteenth century onwards. In this phase, medieval defensive systems faced the challenge of adapting to the widespread use of firearms, while newly conceived ‘modern’ citadels emerged. The study addresses how the castrum was conceived to interact with surrounding urban walls, both in controlling the territory and defending the urban core, across varying altitudinal and geographical contexts—mountainous terrain, river basins, and coastlines. The research adopts a comparative case study approach. Primary examples are drawn from Bergamo—representing high fortifications in the hinterland of the Most Serene Republic of Venice—and Piacenza, which shifted from papal possession to ducal capital in the Po Valley. Further analysis concerns the coastal defences of settlements in the Ligurian Levant, under the jurisdiction of the Most Serene Republic of Genoa. The principal analytical tool is architectural drawing, inspired by the Renaissance sketchbook tradition, allowing systematic comparison of in situ observations, ancient views, and typological prototypes derived from contemporary treatises. The findings reveal consistent structural and strategic integration between castles or citadels and urban ramparts, adapted to specific environmental constraints and political-military demands. Distinct morphological configurations emerge in relation to topographical setting: elevated fortifications in mountainous contexts, riverine bastions controlling valley access, and coastal citadels defending harbours. Although the interplay between castles and city walls has been widely addressed by classical scholarship on fortification history, this study contributes a nuanced perspective on their mutual adaptation during the transition from medieval to early modern warfare. By combining typological, morphological, and functional analyses, it offers fresh insights into the strategic evolution of fortified urban systems, reaffirming the value of comparative and drawing-based methodologies in architectural history.