Introduction: German cities in the world city network

This introduction to the special issue “German cities in the world city network” provides an overview of the current status of research on urban systems in the knowledge economy, with a particular focus on the German urban system. The first part identifies the knowledge economy, particularly the requirements for geographical and relational proximity along the value chain, as a key driver of contemporary urban development. The second part clarifies the concept of polycentricity, distinguishing between its political and analytical roots, while considering its application on different spatial scales. Based on this discussion, the third part emphasizes the importance of relational thinking in analyzing polycentric urban systems and functional urban hierarchies. This is followed by an outline of the specific contribution of each paper to our understanding of the relational geographies of the German urban space-economy.