Since the concept of a smart city was introduced, IoT (Internet of Things) has beenconsidered the key infrastructure in a smart city. However, there are currently no detailed explanations of the technical contributions of IoT in terms of the management, development, and improvements of smart cities. Therefore, the current study describes the importance of IoT technologies on the technology roadmap (TRM) of a smart city. Moreover, the survey with about 200 experts was conducted to investigate both the importance and essentiality of detail components of IoT technologies for a smart city. Based on the survey results, the focal points and essential elements for the successful developments of a smart city are presented.