This paper presents an exercise in the determination of cities from clear and explicit quantitative criteria developed by Eurostat and the DG-Regio. The city concept is linked to the local political level, so in this sense we can talk about «administrative cities», since they are formed by one municipality, or a group of them that are physically contiguous. They are not pure population agglomerations satisfying certain criteria in terms of exceeding a threshold and/or a minimum density. We start from these urban agglomerations, called urban centers, but eventually we link them to municipalities. The main limitations of the analysis are two; on the one hand, the analysis is purely demographic, in the sense that it is the population concentration that eventually determines the number and extend of cities, other aspects such as land cover or the economic structure is absent from the analysis. On the other hand, the proposal is in line with the urban core concept, more than with the urban areas or larger urban zones that includes the urban core and its hinterland. This is so because commuting has not been taken into account in the first stage of the analysis. Building urban centers and linking them to municipalities is accomplished by means of simple Geographical Information System operations (GIS).