SCALE Stockholm uses neighbourhood-scale "Transition Arenas" where civil society organisations and businesses co-create pilot projects for climate mitigation and improved health. The methodology is genuinely bottom-up: the project maps local conditions, engages communities on their own terms, and supports stakeholder- initiated actions — by design, the specific pilot projects were unknown at the outset. Year 1 established four Transition Arenas in Järva, Hammarby Sjöstad/Norra Djurgårdsstaden, Årsta-Enskede-Vantör, and Södermalm/Innerstaden, each themed around local priorities including urban cultivation, energy efficiency, sustainable food, circularity, and sustainable mobility. A major public gathering ("Kraftsamling") brought together 100 participants from 35 organisations, generating 48 ideas. Follow-up gatherings developed these into 25 supported pilot projects. Two districts withdrew during the year, but the design proved resilient. Stockholm's Climate Action Plan, adopted December 2024, directly incorporates the SCALE approach, ensuring the methodology continues beyond the pilot period.