This paper empirically explores the extent to which European cities are on track to sustainable development by examining the environmental performance of a large sample of cities observed during the last two decades. The paper builds on the Environmental Kuznets Curve framework and leverages satellite data to build a set of environmental indicators as varied and as granular as possible. Evidence suggests that European cities are, on average, on track to sustainable development, meaning that the contribution of their economic growth to environmental degradation is already negative or close to becoming so. The paper also examines Transnational City Networks as accelerators of environmental transition. The results suggest that cities participating in such networks anticipate the transition with respect to their peers.