A shift towards a more circular economy is crucial to achieve more sustainable and inclusive growth. Our objective is to provide local and regional authorities with an innovative transdisciplinary open source geodesign decision support environment (GDSE) developed and implemented in living labs in six metropolitan areas. The GDSE allows creating integrated, place-based eco-innovative spatial development strategies aiming at a quantitative reduction of waste flows in the strategic interface of peri-urban areas. These strategies will promote the use of waste as a resource, thus support the on-going initiatives of the EC towards establishing a strong circular economy. The identification of such eco-innovative strategies will be based on the integration of life cycle thinking and geodesign to operationalise urban metabolism. Our approach differs from previous UM as we introduce a reversed material flow accounting to collect data accurate and detailed enough for the design of a variety of solutions to place-based challenges. The developed impact and decision models allow quantification and validation of alternative solution paths and therefore promote sustainable urban development built on near-field synergies between the built and natural environments. This will be achieved by quantifying and tracking essential resource flows, mapping and quantification of negative and positive effects of present and future resource flows, and the determination of a set of indicators to inform decision makers concerning the optimization of (re-)use of resources. The GDSE will be open source. With a budget of €5 million, REPAiR funds a consortium rich in experience in waste and resource management, spatial decision support, territorial governance, spatial planning and urban design, and has deep knowledge of the 6 case study areas. REPAiR is supported by a user board, of key stakeholders for the development of CE as well as local authorities, who are heavily involved in the GDSE testing.