The maritime Rance Valley is a salt basin closed to the north by the Rance dam and to the south by the Châtelier lock, downstream of which the water becomes brackish. It is characterized by its own rhythm of tides as well as by its rocky points surmounted by afforestation which advance on the water creating perspectives specific to the estuary. The shape of the basin, the stalls and the points result from modifications to the layout of the Rance as well as from the different layers with different resistance to erosion and to the microclimates that make up the rocky alignments.