This paper focuses on the issue of ambiance change indicators. A series of guided photo tours was carried out in Nantes (West of France). During this guided tour, inhabitants had to identify the changes in ambiance that they are experiencing. We aim to analyze the indicators that trigger a change of ambiance in an urban environment connected to the density or diversity dimensions that characterize the urban environment. The results show that three levels of understanding of urban environments can be identified: a first level shared by all, a second one shared by social groups, and a last one related to the individual. These three-levels of the inhabitants’ definition of urban ambiance anchors enable us to question participation in urban planning.