Saudi Arabia is speeding up the digital transformation of its urban infrastructure as it works to achieve safer cities, greater efficiency, and objectives set out in Vision 2030. The Internet of Things (IoT) is important since it connects distributed sensors, connected assets, communication networks, edge and cloud platforms, and analytics to operational control. This study looks at how smart-city infrastructure enabled by IoT can improve urban safety and operational efficiency in Saudi Arabia, without assuming that the simple deployment of technology will lead to public value. A structured integrative review of 30 peer-reviewed studies published between 2020 and 2025 was carried out covering the topics of Saudi smart-city development, IoT architectures, edge computing, digital twins, mobility, water, energy, cybersecurity, governance, and citizen participation. The analysis reveals two main pathways for impact. The first is a safety pathway in which sensing, situational awareness, anomaly detection, incident coordination, and robust communications reduce the time taken to detect and respond to incidents. The second is an efficiency pathway in which continuous monitoring, predictive analytics, adaptive control, and asset intelligence cut down delays, minimise resource losses, lower energy consumption, and prevent unnecessary maintenance. It is also found that interoperability, cybersecurity, data governance, institutional coordination, and the establishment of measurable performance benchmarks are essential prerequisites for turning IoT capabilities into real outcomes at the city level. The paper suggests a layered Saudi IoT smart-city framework that links physical assets to decision-making intelligence and operational action, along with an outcome model that connects technical capabilities to safety, efficiency, resilience, and quality of life. The review concludes that the best alignment with Vision 2030 will be achieved when IoT investments are designed around verifiable urban problems, an interoperable architecture, risk-based governance, and outcome-oriented indicators rather than on the number of devices or on isolated pilot projects.