With a growing urban population and an increasing demand in public transport, research into novel public transport solutions becomes increasingly important. Simulation studies can offer an insight into the performance, bottlenecks, and potentials of the public transport system and act as an enabler to improve the efficiency and thereby the passenger experience. With CityMoS, we present a novel methodology for the modelling and simulation of large-scale public transport systems, including passenger assignment, routing, as well as bus and train operation. Contrary to related work in the field, we utilize high-performance parallel computing to follow a microscopic approach, simulating each passenger and vehicle individually to provide more flexibility in the decision-making process.