Many Smart City projects are beginning to consider the role of citizens. However, current methods for engaging urban populations in participatory design (PD) activities are somewhat limited. In this article, we describe an approach taken to empower socially disadvantaged citizens, using a variety of both social and technological tools, in a Smart City project. Through analysing the nature of citizens' concerns and proposed solutions, we explore the benefits of our approach, arguing that engaging citizens can uncover hyper-local concerns that provide a foundation for finding solutions to address citizen concerns. By reflecting on our approach, we identify four key challenges to utilising PD at an urban scale; balancing scale with the personal, who has control of the process, who is participating and integrating citizen-led work with local authorities. By addressing these challenges, we will be able to truly engage citizens as collaborators in co-designing their city.