Abstract: This study examines the fusion of blockchain technology with the internet of things (IoT) in smart cities, exploring how Blockchain's traits like immutability, decentralization, and consensus can address smart cities' concerns. It scrutinizes IoT's applications in smart cities like traffic management and waste control, highlighting data's critical role. It accentuates blockchain's significance in device authentication, securing data integrity, and transactions in a decentralized network. Examining some case studies, it vitrines the benefits of integrating blockchain in smart cities such as optimized operations, enhanced security, and participant trust and confidence. Finally, it demonstrates privacy and security bottlenecks, including energy consumption, scalability, and regulations, emphasizing the need for solutions to overcome these challenges.