The concept of sustainable development and its related principles, in particular public participation, changed dramatically in France the way of developing and implementing public policies for spatial planning. It progressively shifted from sectorial, technical and centralized approaches to more holistic, participatory and deliberative approaches. Individual citizens and social groups in interaction are becoming more numerous and diversified, as well as the habitus and social representations. Thus, getting mutual understanding and a share vision of the territory becomes longer and more complex. In this context, the informational and communicational dimension of these widened socio-technical processes turns to play a central role (Bertacchini et al 2006). To face such a challenge, one of the possible solutions is to introduce mediating objects (Vinck 2006) able to help formulating and making understandable by other participants different kinds of knowledge available among the actors network. This paper deals with a specific communicational artefact, the 3D physical scale-model. That kind of artefact has intrinsic properties suitable for synchronous, face to face and bidirectional communicational processes and it doesn't require heavy decoding tasks (Maurel 2001). It has been widely used in the past centuries by military to prepare the defence or the siege of strategic sites (Warmoes 1997). It is now widely used in developing countries to support participatory development projects (Rambaldi 2002). In France, there is at the moment a clear preference for 3D digital or virtual representations and physical 3D scale-models are rarely used, except for the promotion of urban planning projects. An experiment has, however, been launched in the framework of an operational research study integrated in the spatial planning process of the Thau territory situated on the Mediterranean coast (Maurel 2008). Four different physical 3D scale-models have been co-produced by a network of local environmental NGOs in partnership with the Cemagref and the institutions in charge of the spatial planning processes. These models have been used during different events of the planning process (technical group workshops, public meetings, educative sessions) with various audiences (elected officials, professional representatives, NGOs, public at large, schoolboys). Relying on an IC-tools uses theory (Proulx 2005), this paper aims to focus on various aspects related to the 3D models used in this case study application. It will describe how this innovation has been introduced in the territorial intelligence process, the building process itself and the characteristics of the models, the uses initially planned as well as the observed uses and effects (cognitive, procedural, relational, local capacities). The results indicate that the uses of the 3D scale-models are widely predetermined by the design itself, their immediate surrounding environment and the instructions of use proposed by the designer or the facilitator. One of the most interesting conclusions is that this kind of communicational artefact can greatly help to connect technical representations of the territory with real-life places as perceived by the inhabitants, thus facilitating the dialogue between spatial planners and ordinary citizens.