Metropolises comprise six primary systems that serve distinct domains: governance, environment, mobility, economy, living, and society. These systems work together to create a macrosystem that constitutes a city. In contemporary urban planning, Smart Cities (SCs) have emerged as a means of effectively managing and integrating critical infrastructure, optimizing resource allocation, coordinating maintenance activities, and addressing complex urban challenges while prioritizing security. Over the past few years, cutting-edge technologies like Wireless Sensor Networks, Building Information Modeling, Internet of Things (IoT), Virtual Reality, Big Data Analytic, Artificial Intelligence (AI), Cloud Computing, Blockchain, and Cyber-Physical Systems have paved the way for intelligent and groundbreaking solutions in a variety of industries. Built on the knowledge gained from developing SCs and implementing Digital Twins (DTs) in other sectors, the Urban Digital Twin (UDT) has rapidly expanded in just a few years. UDT technology utilizes real-time data, simulation, machine learning, and reasoning to provide valuable assistance in decision-making processes. However, more than informatization and digitalization practices are required to embrace UDT fully. There has yet to be a comprehensive analysis of how to apply these features of DTs to manage SCs better. This review paper analyzed 150 papers that focused on DT-supported SCs. We aim to identify the drivers, challenges, and future directions for applying UDT-supported technologies. We systematically investigated the characteristics and mechanisms of DTs, categorized different technologies based on their application stages, and identified the key challenges, benefits, and open issues. The findings inform stakeholders in urban management to establish a foundation for future design, development, and widespread adoption of UDT.