This chapter has focused on the importance of 5G networks and other high-end digital infrastructures towards facilitating sustainable smart cities. It looks into big data, AI, and Green IoT (G-IoT), three building blocks that back the trend of intelligent urban services, environmental monitoring, and adaptation strategies in cities. Using case studies and new solutions of technologies the chapter demonstrates how technology can promote sustainability, resilience and quality of life of future cities, through real-time monitoring, green infrastructure, and advanced models of government.