Urbanization and climate change present two challenges to sustainable development, with more than 70% of global CO2 emissions accounts for cities. This review explores the concept of Sustainable Smart Cities (SSC) as a solution to mitigate urban energy inefficiencies and reduce carbon footprints. Drawing lessons from Europe and explores how the integration of renewable energy, smart transportation, and innovative waste management systems could reduce the dependence on fossil fuels and enhance the quality of living. The smart cities with the use of potential technologies such as IoT (Internet of Things), AI (Artificial Intelligence), and smart grids achieve energy efficiency and environmental sustainability. Studying these strategies Sri Lanka (SL), could also contribute to meeting global climate goals. Focusing on stakeholder collaboration, policy reform, and research-driven solutions, this article presents a framework on how transition toward a sustainable urban future in SL can be achieved.