This paper presents a tabletop visualization of relations between geo-positioned locations. We developed an interactive visualization, which enables users to visually explore a geospatial network of actors. The multitouch tabletop, and the large size of the interactive surface invite users to explore the visualization in semi-public spaces. For a case study on scientific collaborations between institutions, we applied and improved several existing techniques for a walk-up-and-use system aimed at scientists for a social setting at a conference. We describe our iterative design approach, our two implemented prototypes, and the lessons learnt from their creation. We conducted user evaluation studies at the two on-location demonstrations, which provide evidence of the prototype usability and usefulness, and its support for understanding the distribution and connectivity in a geospatial network.