This book explores the application of service design to urban commons. It originates from a project developed by the research group of POLIMI DESIS Lab of Politecnico di Milano, aimed at imagining the future of the Reggio Emilia Ducal Palace and its park - the Reggia di Rivalta. The peculiarity of the project lays in the idea that the design of a (public) space should be informed by the design of its services, because the development of specific activities actually builds a fundamental part of the identity of a place, conceiving both the tangible and intangible dimensions as part of a single creative process. The combination of a participatory process and the integration of spatial and service design led to infrastructuring a multi-stakeholder participatory action research of envisioning the future of a public good. This effort has been thus framed into a working methodology, specific tools and progressive outputs, which are defined as Service Master Planning (the process), and Service Master Plan (the product), allowing service design professionals to expand their knowledge and develop skills for a new field of application connected to urban planning.