We reflect on the usefulness and impact of a large-scale tangible participatory mapping activity, drawing on experience from its usage at a national scientific outreach event. The activity was designed to raise awareness of the solar energy transition and gather public perceptions about traditional versus coloured solar panels versus. We gathered perceptions for three types of built environments using an imagined town in Luxembourg called <em>Solartopia</em>. The map was a mashup of three case study locations used in our broader SolarZukunft project, ensuring representation of urban, peri-urban, and rural built environments. Using Lidar data from the national mapping agency, we 3D-printed real buildings at a scale and created a giant tangible map that could be walked upon (3m*4m). We designed a flexible 15-minute workshop activity with six tasks that targeted different abilities, age groups, and interests to ensure it was appropriate for intergenerational participants. The tangible participatory maps sparked curiosity, encouraging participants to observe, interact and reflect. The map fostered simultaneous, multi-group collaboration between researchers and participants, while the visual and tactile elements provided a multi-sensory active learning experience. The creativity and imagination inspired by the map and the tasks suggest an element of social contagion to the diffusion of ideas.