This paper presents an explorative study dedicated to the evaluation of immersive environments engaging different stakeholders that have to collaborate within an innovation process in the area of smart cities supported by a dedicated Fab Living Lab platform. A previous study has unveiled the great potential of close-to-real-life immersion perceived by users/citizens in realistic environments that not only fulfill the " realism " principle of a Living Lab but also greatly contribute to both phenomena of technology acceptance and adoption of the proposed solution. Scholars have previously identified three main factors characterizing an immersive environment: the perceived degree of immersiveness, presence and engagement of users. However, creating close to real-life simulated city environments that provide an appropriate immersiveness, presence and engagement remains a challenge. Furthermore, the traditional working habits of smart cities stakeholders, such as: territorial engineers, town-planners and policy makers, are not prepared for behaving properly in immersive environments. Several experiments were carried out during different events that provided both quantitative and qualitative data through the use of surveys, interviews and observations. For each experiment, several immersive equipment were used. The findings highlight the complementarity between physical and digital technologies supporting co-creation for smart city projects, and the advantage of enabling experts in a field to discover new technologies. Finally, this study provides valuable elements on how to better support close to real-life simulated city environments while providing a higher level of stakeholders' engagement during the ideation of the co-creation stage of the innovation process supported by a Fab Living Lab towards the realization of smart cities.