Smart city is one of the topics most discussed by the researchers. As the world is becoming a global village and more people are moving towards cities it is essential to know the requirements of the cities and upgrade the facilities to make life comfortable. Various technologies like IoT, AI, Blockchain, and Big Data have helped to improve smart city environments. The municipal corporations should provide facilities for residents to make living comfortable. Besides this, the cities should be protected from the impact of increasing environmental pollution, climate change, and global warming. Recent technologies can ensure better living conditions in smart cities through real-time monitoring. The current cities can be converted into smart cities by incorporating the latest infrastructural development and adopting sustainable practices. This paper will study the importance and role of a few emerging technologies in converting existing cities into sustainable smart cities. It will be helpful to learn about how the technologies are being used currently and how they can be applied to make smart cities more sustainable.