The vision of an intelligent city remains ambiguous, with multiple concepts indicating a gradual alignment over time between the ideas of a smart city and a sustainable city. Intelligent cities are considered an evolved concept of urban development, as they combine artificial intelligence and machine learning to form systems that can learn, adapt, and make decisions. A systematic literature review methodology is utilised to define the theoretical scope and to answer the research question. The analysis targeted comprehensive literature covering published topics on intelligent cities over the past twenty years, employing a reproducible and straightforward method to reduce bias by providing verifiable data processing details. The methodology includes identifying studies, explaining the selection process, conducting analysis and synthesis, and deriving conclusions. Eighty-six "intelligent city" papers were analysed by theme, methodology, and results. The literature on intelligent cities covers various topics, such as urban mobility, infrastructure development, risk management, AI integration, sustainability, ecosystems, community involvement, challenges, technological innovations, and inclusive governmental changes.