This chapter introduces of the concept of the fusion of real and virtual worlds creating augmented virtuality by using mobile agents and agent-based simulation technologies. It also introduces the agent-based methodologies addressing augmented simulation and mobile crowd sensing. Fundamental concepts enabling the augmentation of simulation are the concept of digital twin derived from survey data (off- and online) and the concept of physical and computational agents. The simulation world interacts with real-world environments, humans, machines, and other virtual worlds in real time using agent-based modelling and computation. Mobile agents can be used to fuse real and virtual worlds composing augmented virtuality. Agents can represent artificial humans, bots, and machines, and agents can be used for distributed mobile computing, for example crowd sensing. The concept of agent-based virtual sensors and sensor aggregation is introduced with examples from crowd sensing applications. Research and environmental control is only one relevant field of application for the augmented simulation approach.