Historically the development of all medieval fortifications follows the evolution of armaments. Considering that Sorrento was naturally protected, thanks to its position, by the high coast to the north and by the gorges on its western and eastern sides, the defence of the northern side was entrusted to imposing walls. These were interrupted by bastions and towers, the main elements of urban defence. In front of this section of the wall, an external moat was planned to hinder or slow down the advance of the enemy. The moat was filled in from the start of the 19th century, as a result of important urban developments in the city. The defence of the walls was entrusted to 4 ramparts that bore the names of 4 bishops and patron saints of Sorrento. The first was Bastion San Valerio, on the most western side, followed by Bastion Sant’ Antonino, which can still be visited inside; at the extremity of the next section was Bastion Sant’Attanasio also called “di Bagnagatti”, whilst finally, at the edge of the valley was Bastion San Renato.
All the ramparts were equipped with cannons and sentry boxes. During the last rebuilding, during the Spanish period in 1500, the architect followed the second rule for the distance of the ramparts: “that all parts of the fortifications should be within range of a musket’s shot”.