Wireless Sensor Networks (WSNs) are an enabling technology for smart cities, providing the necessary infrastructure for different applications such as traffic management, environmental monitoring, building energy management, and public safety. The integration of WSNs into smart city environments is still a challenge, as it requires dealing with multiple complexities, such as large-scale deployment, limited energy resources and communication capabilities, and the need for real-time data processing and decision-making. With the recent advancements in wireless communication, sensor technology, and IOT, the use of WSNs in smart cities has become increasingly important. However, the development of WSNs for smart cities applications is still in its infancy, and it is important to understand the current state of the art and the challenges that need to be addressed to ensure the successful deployment of WSNs in smart cities. We classify these applications into various categories, and building energy discusses their challenges and opportunities. We also review the existing technologies and standards for WSNs and their suitability for smart city applications. The main contribution of this paper is to provide a clear overview of the current state of the WSNs in smart cities, highlighting the most important trends and challenges for future research. Our survey will be useful for researchers and practitioner’s smart cities, as it will help them understand the current state and future research directions in this field.