In 2015, the German Federal Ministry of Education and Research (BMBF) announced that the Science Year 2015 would focus on the "City of the Future". It called for innovative projects from cities and communities in Germany dedicated to exploring future options and scenarios for sustainable development. Among the successful respondents was the city of Lüneburg, located in the north of Germany, which was awarded funding to establish a community learning project to envision a sustainable future ("City of the Future Lüneburg 2030+"). What made Lüneburg's approach unique was that the city itself initiated the project and invited a broad range of stakeholders to participate in a community learning process for sustainable development. The authors of this article use the project as a blueprint for sustainable city development. Presenting a reflexive case study, they report on the process and outcomes of the project and investigate community learning processes amongst different stakeholders as an opportunity for transformative social learning. They discuss outputs and outcomes (intended as well as unintended) in relation to the specific starting points of the project to provide a context-sensitive yet rich narrative of the case and to overcome typical criticisms of case studies in the field.