Abstract: The metabolism of cities bears important anomalies: high levels inflow of resources and large quantities outflow of (hazardous) wastes. In order to decrease cities' environmental footprint, Girardet (1996) and Rogers (1997) suggested making a transition from a linear to a circular urban metabolism. Even though the concept was coined a few decades ago, it still holds prominence among academics and practitioners (see for instance Newman and Jenning 2008; Lehman 2012; Beatley 2012, van Bueren et al 2012). However, few cities have made such a transition. This shows that creating a circular urban metabolism is complex and challenging. Research so far mainly considered the creation of a circular urban metabolism as a technical process. We would like to argue that organisational and institutional aspects of such process are also important for understanding why there are implementation gaps. However these have been understudied. This paper tries to bridge this gap by adopting a different conceptual approach. We consider that the creation of a circular urban metabolism passes through multiple innovation processes. Such processes happen in a systemic manner wherein, not only technical but organisational and institutional solutions and changes are adopted and adapted. In this paper we conceptualise the circular urban systems, as a robust concept to address the anomalies of the metabolism of cities. We discuss how this concept is different from existing one and why we think it can help in better grasping the challenges ahead. We also focus on the kind of insights that can be gained by adopting this new conceptual understanding and how this can open a new agenda for future research.