The presentation is hinged on my doctoral research, which seeks to understand the evolution of a city along the entire duration of its existence (Gravier, 2018). This research is built upon the case study of Noyon, a French city founded in the 1st century AD. My approach can be synthesized in three stages. First, I assess the functional intra-urban structure to establish the trajectory of the city over 2000 years. Then, I identify the relative position of the city within the system of cities it interacts with. This position is studied in terms of political, administrative and economic features. Finally, by confronting the intra-urban trajectory and the relative position of the city, we can investigate to what extent the history of a city and the history of the other cities of the system are united. The vastly long term considered raises two main issues. First, the societies studied over 2000 years are highly distinct. Comparing them involves questioning the consistency of the definition of spatio-temporal entities, in order to study their trajectories. Second, this method requires working with archaeological, textual and iconographic data, which are sporadic and scarce, especially when studying large scales processes. This turns a large part of our research into an investigation where many clues have to be collected in order to retrace some long-disappeared spatial configurations and facts. All of this requires new methodologies, along with a need to delineate unambiguously the paths relative to knowledge building, in order to offer a reproducible study of cities in systems over the long term. I will expose these paths, punctuated by seven main steps. The first two steps refer to intra-urban level analyses. First, I build basic units of urban space. Each unit is defined by a function, a location and a duration in time. The conceptual framework of those basic units inherits from researches driven by archaeologists working on intra-urban level (inter alia, Biddle et al., 1973; Galinié and Rodier, 2002). Besides, these units are compiled in a relational database and, as a second step, these data can be easily processed to capture the trajectory of the city. Then, steps 3 to 6 refer to analyses linked to the system of cities level and inherit from researches achieved by geographers (inter alia, Berry, 1964; Bourne and Simmons, 1978; Pumain, 1997; Bretagnolle, 2009). Step 3 allows delineating the scope of the study zone by territorial and network approaches, within which the cities potentially in interaction with Noyon are contained. Steps 4 to 6 affords us to examine the relative position of Noyon within the system of cities it interacts with. Two main difficulties emerge at these stages: 1) Geographers often study interactions between cities for the purposes of defining systems thanks to human or merchandises flows. However, data linked to ancient periods usually do not allow us to quantify flows, but only to inquire about the presence or absence of relations. In order to identify interactions, I decided to combine several case study related to these relations at different times. 2) The relative positions of the cities in a system are commonly observed through spatial position and size. Yet we do not have uniform data concerning population size before the beginning of the 19th century for France. Consequently, I decided to create population estimations from urban areas thanks to a statistical model (step 6). The obvious underlying assumption of this model is that urban area is a proxy measurement of population. Thus it is necessary to discuss the form of the relation between those variables for the cities located in the study zone (step 5). Finally, step 7 is the synthesis based on all previous steps. It allow us to propose new explanations on structural processes and events underlying the evolution of Noyon over 2000 years. Berry, B. J. L. 1964 ‘Cities as systems within systems of cities’, Papers of the Regional Science Association, 13(1), pp. 146–163 Biddle, M., Hudson, D. and Heighway, C. 1973 The future of London’s past: a survey of the archaeological implications of planning and development in the nation’s capital. Worcester: Rescue Bourne, L. S. and Simmons, J. eds. 1978 Systems of cities: reading on structure, growth, and policy. New York: Oxford University Press Bretagnolle, A. 2009 Villes et réseaux de transport : des interactions dans la longue durée (France, Europe, États-Unis). Université Paris I, Habilitation à diriger des recherches. http://halshs.archives-ouvertes.fr/tel-00459720 Galinié, H. and Rodier, X. 2002 ‘TOTOPI: TOpographie de TOurs Pré-Industriel, un outil d’analyse urbaine’, Les petits cahiers d’Anatole. Tours, 11. http://citeres.univ-tours.fr/doc/lat/pecada/F2_11.pdf Gravier, J. 2018 Deux mille ans d’une ville en système. Proposition d’une démarche appliquée au cas de Noyon. Université Paris I, Thèse de doctorat sous la direction de L. Sanders et de N. Verdier. http://frama.link/gravier_these Pumain, D. 1997 ‘Pour une théorie évolutive des villes’, Espace géographique, 26(2), pp. 119–134. http://www.persee.fr/doc/spgeo_0046-2497_1997_num_26_2_1063