CityMoS is a next-generation mobility platform capable of high-performance, agent-based, microscopic simulation of city-scale transport systems at high resolution, including private, public, and commercial transport. CityMoS can be used to support the transition to electric vehicles, the design of novel intelligent transport system solutions, the introduction of new modes of public transport, or the mitigation of traffic emissions such as carbon dioxide or heat. It focuses not only on traffic patterns but on the mobility of individuals and utilises a modern computer science approach to push back the frontiers of microscopic simulation by balancing accuracy, scalability, and performance.