Ultra-high-resolution wall-sized displays feature a very high pixel density over a large physical surface, typically covering a few square meters. They provide effective support for collaborative work sessions that involve the visualization of large, heterogeneous datasets. But the development of interactive visualizations for ultra-highresolution wall displays raises significant challenges. These range from the design of input techniques adapted to such surfaces, to the design of visualizations that effectively leverage their extreme display capacity. Challenges lie not only in the design but in the technical realization of these visualizations as well, as they run on computer clusters and thus require dedicated software frameworks for the distribution and synchronization of data and graphics. In this talk, I will essentially focus on challenges that relate to the engineering of interactive visualizations for cluster-driven wall displays, discussing different approaches that we explored over the last fourteen years to create geospatial visualizations and the associated multi-scale interaction techniques.