The world's population is constantly growing, and most of the inhabitants are moving to urban areas, which are cities. Cities are becoming overcrowded and there is less and less space, and the needs of citizens are increasing. This paper analyzes the concept of city development, with an emphasis on smart cities and sustainable development. The concepts of the city, smart city and sustainability are defined, as well as how cities adapt to changes in the environment, climate change, and how to implement modern technology in their everyday life. The importance and characteristics of sustainable urban development are discussed, as well as ways to accomplish them using smart technology. The paper analyzes various current examples of effective sustainable strategies for the development of smart cities. It states that the success of smart cities requires high-quality infrastructure support, as well as raising citizens' awareness of the importance of technology and quality coexistence with it, respecting the historical aspect and the basic role of cities. The world's cities are increasingly applying sustainable development strategies and using renewable energy sources in order to use all the advantages of technological progress in the management of their resources in the best possible way.