In the era of communication, the participation in internet-communities has grown to become a motor for innovation in software and community platforms. The paper describes the hypothesis that, by creating a virtual city (or a second city) a new type of social, economic and scientific network is established, which is supported through visual communication technologies. The various users bring, per se, their own intrinsic motivation and requirements to the system. Nonetheless, a personal identification with a city/neighbourhood/house/apartment can be used to awake awareness and to foster participation. This is especially important when dealing with the city inhabitants. City modelling itself has been carried out for over a decade. Projects such as the city model of Graz have shown how city models can be established so as to be scalable for new information (Dokonal et al 2000). Furthermore, these city models have been used in the education of future architects and urban planners. The project described here moves in the opposite direction: the model moves out of the classroom to an interdisciplinary city-model-platform. The work described here is the conceptual model for a multi-dimensional data set that models the city. This has spawned a host of other projects using the model as a foundation for further interactivity development and the extension of the model itself. The paper describes the structure of the conceptual model and the first experience of incorporating diverse projects such those mentioned above. The model also is structured so as to be compatible with the XML standards being developed for city information (CityGML). The goal of the project is to create a data set describing the city that not only describes the geometry, but also the history (including planned histories) and nature of the city. In contrast to virtual realities, which attempt to create a separate world (e.g. Second Life), the Second City is intended as an interdisciplinary repository for the geometrical, historical and cultural information of the city.