The cumulative dissertation project tries to approach the topic of critical infrastructures with different approaches. Central aspects are "space" and "scale". First, the perspective of the nation state is examined, because nation states define sectors and infrastructures that are considered critical; they thus have a formative role. Then, the city level is examined as a planning unit, because decisions are also made at this level that influence the nature and functions of infrastructures. Finally, we zoom into the health sector in hospitals, because processes and decisions that change infrastructures also take place here.<br/>Critical infrastructures are inherently potentially affected by failure events, because "critical" refers to the possible failure of infrastructure. Therefore, concepts that guarantee maintenance occupy a special position. In Germany, the focus is on the protection concept, whereas in Nordic countries such as Sweden, resilience is significant as a concept.