The system of fortifications that rings the old town of the city of Otranto (Puglia, Italy) conserves the still visible traces of structures belonging to various historical periods, attesting to the evolution of the settlement’s defensive system from the Messapian period (fifth century BC) to the Aragonese period (sixteenth century). As part of a recent urban renewal project targeting the area of the moats, new archaeological, historic and architectural investigations were conducted. These included a painstaking analysis of the circuit of defensive walls and the broad and deep moat, which contains valuable archaeological and architectural evidence that has never before been studied. The use of advanced surveying technologies such as 3D Laser Scanners, parametric and georeferenced, enabled a holistic, synoptic and comparative reading of the structures, recording the distinctive features, building techniques, materials, alignments, range of thicknesses and losses of continuity in the walls, all of which are necessary for a correct identification of the construction phases. In addition, the data arising from the study and three-dimensional survey of some subterranean tunnels, entirely excavated in the rock in the area of the moats surrounding the Aragonese castle, have also enriched the framework of knowledge regarding specific military and defensive dynamics.