The study of a city over long time spans (longue durée) is based on knowledge of the topographical elements and their relationships with each other from the beginning of human settlement to the present day. As archaeologists, our aim is to work on the processes of change of the town. To that end, we must look at the heritage, inertia, trajectories and dynamics of each object making up the town. These can be looked at under three headings: social use; location and surface area; duration and chronology. Our procedure is part of a conceptual approach which concerns historical sciences, geomatics and informatics on account of its simultaneous consideration of the longue durée and multiple temporalities. The objective is to put forward a way of modelling "historical objects" (cfr. infra § 2), the subject matter of our study, which will help create geo-historical databases from which it should be possible to: - provide a vertical and horizontal perspective of the phenomena (What happened at a particular time? How did a particular place evolve?); - produce as many inventories as possible; - express the change of state (and thus the inherent process); - preserve the specific nature of each place, i.e. its social, temporal and spatial mutations; - avoid redundant information, in order to facilitate data analysis and management; - represent a single reality in a variety of ways (depending on the accuracy and quality of information available).