To face the challenges of metropolisation and post-carbon society, cities work on the Sustainable City of tomorrow. It must be first a city serving the people, by being adapted to their changing ways of living. USER aims to link-up urban regeneration and conditions for an effective sustainability by a multi-dimensional approach involving residents and users of the city. USER will focus on the role of public spaces to make a more (convivial, secure, friendly and efficient) liveable City.