This report 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. It identifies a number of barriers to scale up of NbS in cities, including: need for improved multi-level governance, lack of business models and financing, and insufficient valorisation of nature as assets.