Challenge Whereas many tools for e-participation have been developed to involve citizens and large stakeholder groups, there are no digital instruments which enable the creative participation of the citizenship on a massive scale. The paper presents the blueprint for a new co-design environment to enable communication and collaboration between large numbers of citizen and professional experts, developed in the course of a joint project of TU Dresden, TU Delft, and ISEN Toulon in cooperation with German and French software companies. Approach Key novelty is a Public Project Space for non-professional civic users – a highly accessible, low-threshold public interface, a Project Play Ground which features highly experiential design tools for citizens who want to engage actively in the design process. Second novelty is a collaboration platform which connects the Project Play Ground to professional urban designers. This Co-design Workspace is to function as a unidirectional exchange hub between public users and professionals to support the collection of project relevant information, the generation of initial impulses, and the discussion of propositions in the early phase of the design. Findings As key catalysers for co-design and communication, the blueprint suggests Moderated Models (MoM) that are exchanged and iterated between professionals and the public until mutual understanding is found. The Moderated Models are conceived as derivatives from a cloud-based Project Information Model (PIM) which integrates all project relevant information, including technical data as well as public input. Moderated models are published in the public Project Play Ground as to stimulate feedback e.g. via Social Media. Impact An essential functionality of the co-design environment will be the assessment of proposals on semantic and emotional level, in order to devise early detection of resistance against projects, and to prevent the build-up of negative public sentiment. The co-design environment will enable professional creatives to utilise the public´s creativity, to follow public opinions and sentiments, and to derive design intelligence from them. The design and decision making process will be informed and transformed by impulses of “citizen experts” as a driving force.