This compendium connects together the key themes of nature, cities and innovation. It discusses how to assess what nature-based solutions can achieve in cities. It examines how innovation is taking place in cities. And it analyses the potential of nature-based solutions to help respond to climate change and sustainability challenges. This compendium combines both technical knowledge and the social sciences to better understand nature-based solutions in a holistic perspective. New governance arrangements, business models, financing and forms of citizen engagement will be needed to make the promise of nature-based solutions a reality.