This chapter summarizes and reflects upon some of the most pertinent particularities of urban transitions, and evaluates them with regard to their potential for institutional change. It reflects on some of the most important characteristics of cities, and discusses their relevance for processes of institutional change. A central assumption about cities is that they are often able to provide the intellectual, financial and political resources necessary to develop initiatives and blueprints for sustainable change. Despite the high path-dependency and rigidity of cities, there is also evidence that urban spaces could serve as exemplary niches of how to address and govern sustainable change, because they possess favorable socio-technical structures that enable the creation of new sustainable practices. It can be argued that the particularities of urban spaces simultaneously provide opportunities and challenges for sustainability transitions. The characteristics of cities described in the chapter point towards the distinctiveness of urban sustainability transitions.