A system for generating a virtual gaming environment based on features identified within a real-world environment, and adapting the virtual gaming environment over time as the features identified within the real-world environment change is described. Utilizing the technology described, a person wearing a head-mounted display device (HMD) may walk around a real-world environment and play a virtual game that is adapted to that real-world environment. For example, the HMD may identify environmental features within a real-world environment such as five grassy areas and two cars, and then spawn virtual monsters based on the location and type of the environmental features identified. The location and type of the environmental features identified may vary depending on the particular real-world environment in which the HMD exists and therefore each virtual game may look different depending on the particular real-world environment.