As climate change develops, with most of the world population living in urban areas, decarbonisation of cities is among the greatest challenges of the coming decades. In the framework of the EU City-zen project, a number of so-called Roadshows has been organised in ten cities within and outside Europe in order to plan and kick-off their transition towards an energy- and climate-neutral economy. During the Roadshows, a group of experts is engaged to perform co-working activities and participative labs involving local stakeholders. These activities support cities in identifying their own decarbonisation pathways, mainly by combining three mutual processes, i.e. energy design, urban design and carbon accounting. The latter, in particular, has been used to quantify the greenhouse gas emissions of cities and neighbourhoods and to estimate the mitigation effect of a combination of measures towards the desirable condition of carbon neutrality. This exploratory and proactive design process has been successfully demonstrated through intensive workshops and can be potentially replicated in other cities. This paper provides a schematic overview of the main results achieved in the Belgian town of Roeselare, but more significantly it describes the techniques needed to make that cooperative process understandable, impactful and implementable. It is likely that 2050 European goals will drastically change urban environments and socio-economic dynamics in cities, due to the fragmentation of energy sources. Hence, from this standpoint there is a vital need for integrated technologies and infrastructures, a circular economy and community-based processes such as food production, sharing of facilities and valorisation of ecosystem services. The City-zen Roeselare Roadshow brought over 300 stakeholders into the process of re-imagining and visualising their 2050 future city with these solutions. Stakeholders, with no particular expertise in carbon accounting or sustainability, would now have the capability of understanding and ...