Conclusions and perspectives Rooftop architecture represents an opportunity to support urban regeneration and concentration processes, in the perspective of reducing land use, encouraging ecological requalification of the existing, forerunning new vertical cities. An interesting case study is the Rotterdam experience, where the Municipality - with the operational support of De Urbanisten - started in 2015 a pilot project to test innovative methods for managing and controlling the development of the "top spaces" of city, exploring their potentialities for housing, environment and landscape. The plan is based on the definition of four categories, which are associated to buildings according to their position and their technical, structural, functional characteristics - "green" roofs for agricultural use, "blue" roofs for collecting and cleaning water, "yellow" roofs for producing sustainable energy, "red" roofs consists in the attempt to control the whole process through an organic vision, determining the destination of every single building in relation to its social and physical context, preventing the chaotic spread of interventions and favoring a clear development of 'urban decorum. On the one hand, the Italian situation is worsened by the presence of fragmented bureaucratic apparatus, which means a large number of decision makers - commissions, regional and local authorities, superintendences etc. - leading to stagnation and lack of incentives to innovation and research.