IT architecture forms the digital core of contemporary organisations; thus, architecture work directly concerns the transformation of these organisations. The literature on architecture work and architecting has identified the principles, styles and characteristics that define the policy ideals of architecture work and has demonstrated how these drivers play out in real-world projects. With an in-depth case study, we add to this literature by investigating the multilevel challenges that architects address in transforming large-scale infrastructures and how major challenges come to the surface during the architecting process. Our empirical evidence comes from our longitudinal investigation in a large health region in Norway. We offer two contributions. First, identification and a rich description of three modes of architecting framed as functional, spatial and temporal dualities. Second, we integrate the empirical data into a process model and theorise how contextual and professional drivers are transformed through the architecting modes and form the actual results.