Realistic virtual worlds are increasingly used for training, decision making, entertainment, and many other purposes, which require the convincing modeling and animation of virtual characters as well as the faithful behavior of devices in their environment. Intelligent Simulated Realities (ISReal) is a platform for virtual environments that are enriched with a high-level semantic description and populated by intelligent agents using Semantic Web technologies to perceive, understand, and interact with their environment. In this paper, we present the basic architecture of the ISReal platform and show the user interaction in an agent assisted learning scenario.