<p>A 3D city model is a representation of an urban environment with a three-dimensional geometry of common urban objects and structures, with buildings as the most prominent feature. In the last decades, 3D city models appear to have been predominantly used for visualisation; however, nowadays they are being increasingly employed in a number of domains and for a broad range of tasks beyond visualisation. The MUIF (Modello Unico dell’Infrastruttura Fisica) project, here illustrated as a case study, refers to the implementation of a single spatial model of the infrastructure of Italy’s railway system (RFI).</p><p> The authors describe preliminary results and the critical aspects of the study they are carrying out, explaining the processes and methodology to model all datasets into a single integrated spatial model as the reference base for future continuously updates. The case study refers to data collected by different sources and at various resolutions. An integrated spatial Database has been used for modelling topographic 3D objects, traditionally implemented in a 3D city model, as well as other specific 3D objects, related to the railway infrastructure that, usually, aren’t modelled in a 3D city model, following the same methodology as the first ones.</p>