Abstract
<jats:p>The rational of this chapter is to explore the role of Digital Twins (DTs) in enhancing smart city Internet of Things (IoT) applications. Furthermore, the chapter investigates how Digital Twin (DT) technologies might improve the sustainability, functionality, and efficiency of IoT applications within the framework of smart cities. Moreover, the incorporation of DTs presents the opportunity to model, track, and optimize intricate urban systems in real time as cities grow more networked and data-driven. Additionally, in order to evaluate the creation, implementation, and effects of DTs across international smart city projects, the research conducts a thorough literature review of scholarly and empirical studies published between 2015 and 2025, relying on more than 120 peer-reviewed articles, technical reports, and policy documents. Subsequently, the chapter focuses on five prominent smart cities, namely: Helsinki, Amsterdam, London, Singapore, and Barcelona which have led the way in implementing DTs in urban infrastructure, mobility, energy, and public services.</jats:p>