The author examines the influence of various structures born from the civic community in the urban centrer of Nantes on public policies: Institut Kervégan since 1977, consultative conferences since 1996; Development council, journal "Place publique" since 2007. He tries to measure their influence on the decision of elected representatives, as much about the agencement of the territories, the management of the urban center, the choice for structuring infrastructures. He confirms that the changes put in motion by the elected representatives are spurred by the reflexions of the civic community.