The volume collects the materials and contributions developed within the OC Open City International Summer School, which was held from 2009 to 2019 at the Polo Territoriale di Piacenza of the Politecnico di Milano, with the presence of more than 100 students and 50 hosts a year, who have engaged on salient issues of the contemporary architectural and urban planning debate. The volume also published the results of the OCiam International Consultation, exhibited in the spaces of the 'Fragile Landscapes' exhibition, which took place during the last session of the Workshop, in September 2019. The latter, which saw the presence of national guests and internationally renowned, has been divided, as can be read in the volume, into three main chapte...