3D city models are mostly seen as static or at least as background for various animations types. In the last couple of years, experts have realized that 3D city models (technical maps of the future) should be maintained in order to be used in a continuous and dynamical planning and administration. Therefore it is important that temporal information is attached to the different parts of a city model so that it can be used as part of metadata for city models. Another and just as important use of time is related to the temporal characteristics of the 3D city models. There is a huge difference between traditional static city models and those models that are built for realtime applications. The difference between the city models applies both to the spatial modelling and also when using the phenomenon time in the models. If the city models are used in visualizations without any variation in time or when the variation in time is non-synchronous with real-time, usually more effort can be put on the fi delity in relation to the aesthetic and geometric representation. This means that the models are more realistic or contain another level of detail. However, if one looks at virtual environments with an in-built dynamic or a model suitable for visualization in realtime, it is required that modelling is done with level-of-detail and simplification of both the aesthetics and the geometry. If a temporal characteristic is combined with a visual characteristic, the situation can easily be seen as a t/v matrix where t is the temporal characteristic or representation and v is the visual characteristic or representation.