Cities worldwide are growing fast, compromising their surrounding landscapes, and consuming too much of scarce resources. At the same time, due to the changing climate, temperatures in cities are rising and weather extremes have become the new normal. Most (western) cities are facing a worrying loss of biodiversity, and inhabitants are more and more alienated from daily experiences of nature, the environment and food. To be liveable in 30 to 50 years, cities have to face these challenges and it is inevitable that they develop towards liveable green sustainable circular systems. This Special Issue focuses on the transition that this involves: which combination of social and ecological changes should take place and how can we prepare ourselves for these changes?