With the rise in population of urban areas, there is a need for innovative solutions that are able to solve the problems related to this growth. Air pollution, increasing energy consumption, health risks, safety risks, and inefficient government services are some of the issues, cities might have to face when growing bigger and bigger. Many of these can be solved by modern technologies and concepts, which are incorporated in smart cities. In the following article, we want to share details of the 10 smartest cities in the world and what their critical success factors are. To rank them, we rely on the Smart City Index 2020 by IMD.