Digital Twin (DT) technology is developing as an important tool for cities to solve significant environmental concerns by providing real-time insights and data-driven solutions. As urban populations continue to grow, the need for environmentally friendly city planning has reached new heights. This research investigates the use of DT for monitoring critical environmental indicators such as waste management, water consumption, and air quality. Cities may use real-time data from sensors and IoT devices to analyse environmental indicators, anticipate trends, and enact more sustainable policies. The article also discusses many case examples in which DT effectively supported sustainability programs while addressing issues like as data interoperability, scalability, and privacy. Finally, this study emphasizes the ability of digital twins to create more resilient, sustainable, and habitable urban settings.