The Saint-Etienne Higher School of Architecture (ENSASE), in partnership with the association Carton Plein proposes the Carnot viaduct as a playground of pedagogical experiments. Students from the Master's course "Public Spaces: design, architecture, practices" (Jean Monnet University, Saint-Etienne, ENSASE and the ESADSE), from the "Laboratoire hors des murs" (Master's course at the School of Architecture), and from the "Atelier U27" of the La Cambre-Horta Faculty of Architecture, Bruxelles, work together in a workshop to invest the chinks and the cracks around the viaduct in the form of micro-constructions, questioning aspects of urban planning.