The concepts of metabolism, ecosystems, and circular economy are currently challenging the discipline of urbanism. As the shift from linear to circular production-consumption patterns seems to be ultimate for reducing the externalities of our urban environments and to meet stricter environmental targets, the search for sustainable territorial metabolism has become imperative for our metropolitan areas. This publication questions the European foundation of urbanism in relation to the challenge of territorial metabolism and combines theoretical contributions with cutting edge design proposals for European metropolitan regions. It synthesises two years of intensive research by design in Barcelona, Brussels, and Veneto conducted jointly by the Laboratory on Urbanism, Infrastructure and Ecology of the Universite libre de Bruxelles (ULB), the Instituto IUAV di Venezia and the Laboratori d'Urbanisme de Barcelona (ETSAB).