Based on a detailed mapping of urban challenges and relevant nature-based solutions (NBS), Nature4Cities aims at developing complementary and interactive modules to engage urban stakeholders in a collective-learning process about re-naturing cities, develop and circulate new business, financial and governance models for NBS projects, as well as provide tools for the impacts assessment, valorisation and follow-up of NBS projects. The different modules are:• a database of generic NBS and associated environmental, economic and social performances • an observatory of NBS projects best practices / case studies • a set of innovative business, financial and governance models for the deployment of NBS in a range of different contexts, together with a tool to help urban stakeholders identify eligible models regarding their NBS project contexts • a NBS project impact assessment toolbox providing capabilities for environmental, economic and social impacts evaluation at different stages in the project development cycle from opportunity/feasibility studies to design steps and project follow-up). This toolbox will built on a range of tools, from generic indicator-based assessment for early project stages, down to detailed modelisations of NBS behaviors.These modules that already have a proper purpose on their own, will furthermore be integrated in a NBS dissemination and assessment self-learning platform [N4C Platform] to assist NBS project developers along the entire life cycle of their projects from opportunity studies and project definition down to performance monitoring.Nature4Cities indicators, methodologies, tools and platform will be field tested in real working environments and on real nature-based solution projects and developments in selected cities in Europe, which will be partners of the project and engage their technical urban and environmental planning teams.