Space in online virtual worlds only exists as an experience. This chapter explores this experience by seeking to understand the nature of virtual worlds, both online and offline, as well as of the space they seem to create and present. This investigation also engages in an analysis of the nature of virtuality itself, along with the various ways by which it can be understood, the open philosophical questions it appears to address, and the various diverse phenomena it attempts to describe. Accordingly, this chapter delineates the distinct aspects of virtuality and how they each contribute to the formation of online virtual worlds. Finally, it shows the experience of space in online virtual worlds to be the result of a superposition of multiple, separate phenomena, including the creation of pictorial illusions throughout the history of art, the advancements of digital technology and online connectivity, as well as the process of forming mental constructs from the perceptions of objects in the external world and of learned concepts about them—all coalescing into a unified experience.