In the GRAAD project we aim at developping a knowledgebased system which manipulates spatial and temporal knowledge while simulating the kind of behaviour that people adopt when describing a mute. A route description is essentially a narrative text in which sentences are prescriptions given by the speaker to an addressee: they describe a succession of actions that the addressee will have to carry out when s/he follows the route in the described environment. Hence, temporal and spatial knowledge are "interleaved" in a route description. In this paper we present an approach for generating route descriptions using spatial conceptual maps and a simulation of the virtual pedestrian’s movements in these maps. We show how the notion of influence area enables us to transform spatial relations of neighborhood and orientation into topological relations. A way can be partitioned into a succession of certain typical segments (intersection with other ways, intersection with crossable objects, intersections with landmark objects’ influence areas) which are well suited for natural language descriptions. A route is specified as a succession of way segments pertaining to one or several ways, some of them being used to generate the natural language description. We show how the equations of the virtual pedestrian’s trajectory can be used to select the proper movement verbs used in the route description.