Many subgroups in the US remain marginalized from, misunderstood by, or invisible to the larger communities they reside in. Technologies supporting community building, more generally, have focused on apps; but these apps can fall short of making visible and heard subgroups such as the LGTBQ+, immigrant, and black populations. In response to this shortcoming, we report on the design iterations and evaluation of communIT, a cyber-physical platform for making visible and heard, in public places, subgroups towards building community. To inform the design of communIT, we conducted in our lab a design studio study (N=57), a co-design activity with a to-scale prototype (N= 12), and a co-design activity with a full-scale prototype (N=28). These lab studies involving in-person participation by local university students and public high school students were followed by an online study (N=197) reaching out to subgroups across the US. We learned the following and more from these studies: preferences for communIT’s design characteristics (i.e. form, embedded IT, and function); that communIT may be suitable and useful for diverse groups to share, engage, 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 making subgroups visible and heard towards community building.