Stone sentinels: the coastal towers of Forio d’Ischia

The contribution presents a study of the coastal defensive system of Forio, on the island of Ischia, with particular attention to the towers and their integration into the historic urban fabric. The aim of the research is to create a digital twin of Forio’s historic center as a tool for analysis, enhancement, and protection of its architectural heritage. The towers, now deeply embedded within the built environment and often unknown to both residents and tourists, represent the "stone sentinels" of a complex defensive system. The analysis begins with a macroscale reading of the coastal defensive belt of the Mediterranean, which developed between the Middle Ages and the early modern period in response to pirate and Saracen raids. It then focuses on the coastal stretches of Campania and Lazio through a georeferenced survey conducted in a GIS environment. Another important aspect of the research is the documentation of Ischia’s defensive system—castles, towers, batteries, and guard posts—which plays a strategic role within the Phlegraean archipelago. Within this framework, Forio stands out as an emblematic case of a fortified village. Using historical sources such as Jakob Philipp Hackert’s 1789 view and photogrammetric surveys of the ten identified towers, supplemented by LiDAR data, the system has been precisely mapped and the data processed into 3D models, architectural sections, and elevations. The digital model emerges as an essential tool for understanding, managing, and preserving the territory in a geologically fragile context such as Ischia and serves as valuable support in emergency scenarios and post-earthquake reconstruction efforts.