This paper advances research on external urban relations by drawing attention to the role of temporary project-based economic organisation in the formation of inter-firm links between cities. Through a novel empirical examination of (trans)national co-production in the motion picture industry, we reveal how such projects transcend the boundaries of individual production clusters and link urban centres within specific network configurations. Stripping away the 'top layer' of Hollywood's commercially successful feature films, we undertake a social network analysis of film productions in four markets across three continents-China, Germany, France and Brazil-to provide a unique comparative analysis of networked urban geographies. Our findings show that film production networks are grounded in existing structural relations between cities. The spatial forms of these networks range from monocentric in the case of the French film market, to dyadic in the case of China and Brazil, to polycentric in the case of the German film market. Conceptually, we argue that adopting an inter-firm project-based approach can account for the ways in which complex patterns of inter-firm production relations accumulate to form (trans)national city-networks. Viewing city networks in this way provides an important alternative perspective to dominant conceptualisations of global urban networks as formed through corporate intrafirm relations.