In combination with the rapid technical improvements of computers, building large virtual scenes has become a popular field in computer graphics. Often, within a real reconstructed city, a building that has disappeared, or a virtual town, virtual humans populating these scenes are expected to provide a feeling of real life. Our specific aim is to populate these scenes with virtual humans in order to offer assistance in decision making concerning urban infrastructures. In this view, we have to integrate the problem of planning human actions and behaviour for urban life simulation into a virtual town. We present an informed environment, which corresponds to a database dedicated to urban life simulation. We discuss the use of a database, and methods and tools for creating and providing the information necessary for animating virtual humans in a city. The informed environment is based on the hierarchical decomposition of an urban scene into environment entities providing geometrical information as well as semantic notions, thus allowing a more realistic simulation of humans. In this manner, virtual humans can be provided with a certain kind of urban knowledge. Moreover, the database can offer other types of services for scene creation for example