Cities are engines for development and provide opportunities for innovation and interaction. But cities can also exacerbate some of the world’s most serious environmental and socioeconomic challenges, and at the same time citizens and urban infrastructure are facing vulnerable. For cities to make peace with nature, we need to plan and design cities and urban infrastructure with nature in mind. Nature-based Solutions (NbS) can help cities address urgent and fundamental environmental challenges by bringing ecosystems services back into cities and rebalancing cities’ relationships with their surrounding areas. By accelerating the implementation of NbS, decision-makers can help cities adapt to effects of climate change, reduce urban heat island effects and cooling needs in buildings, clean air, manage water. This report, produced by UNEP in close collaboration with the Italian Presidency of the G20, investigates the potential of NbS to help build smart, sustainable and resilient cities, drawing from more than a decade of research and experience from G20 countries and beyond. It offers an overview of the best practices of NbS implementation in cities around the world, and a set of guiding principles to improve territorial governance and establish multi-level governance frameworks to increase the impact and coherence of policies and private investments. The goal is to inspire further action by national governments and city authorities to enhance NbS in cities to reduce their vulnerability to climate change. In this framework, Covid-19 recovery plans offer a great opportunity to scale up NbS in cities, with a view to building back better in ways that protect, conserve, and restore our ecosystems and their services, while addressing the social and economic challenges of urban areas and significantly reducing environmental impacts.