Many subgroups remain marginalized from their larger communities. Technologies supporting community building have focused on apps, but many apps fall short of making subgroups such as the LGTBQ+, immigrant and black populations visible and heard. We report on design iterations and evaluations of communIT, a large-scale, cyber-physical platform for helping subgroups build community by making them visible and heard in public places. We conducted a design studio study ( N = 57), co-design activities with to-scale and full-scale prototypes ( N = 12 and 28), and an online study ( N = 197). We learned: preferences for communIT’s design; that communIT may be suitable and useful for diverse groups to engage, share, and interact; that communIT may make an impact on how the larger community perceives diverse groups; and that communIT may be helpful for groups to express their ideas, concerns, and aspirations to the larger community. Our research suggests the promise of large-scale, cyber-physical artifacts for building community.