With the invention of advanced technologies, there are millions of options to improve the quality of life in an urban city. Several innovative implementations transform urban cities into smart cities using new technologies to enhance urban inhabitants’ efficiency, sustainability, and overall quality of life. Our study shows that knowledge graphs play an important role in smart cities for transportation, parking, traffic, and city development. They serve as significant repositories, bringing together data from various sources. Several crucial domains of smart cities use knowledge graphs to resolve challenges that hinder urban development. In this paper, we discuss the applications of knowledge graphs in various smart city areas, identify existing challenges, and propose strategies to enhance the current implementation of knowledge graphs in smart cities. We highlight a few innovations that used knowledge graphs in smart cities, showcasing their versatility. Integrating knowledge graphs into smart cities significantly enhances the efficiency of urban services by consolidating and connecting data from different sources and constructing a graph, aiding in better decision-making. © 2024 Copyright held by the owner/author(s).