In the writing classroom, collaborative learning often takes the form of coauthoring, peer workshops, or critique sessions. While these are useful, what other active-learning approaches might be effective, particularly in light of the range of media with which students are increasingly familiar? World building--creation of an alternative/speculative or futuristic land, world, or universe--offers an approach to fiction writing amenable to both creative collaboration and digital modalities. This article examines how a team-based world-building project in an advanced writing course leverages both physical and virtual space as creative collaborative environments by building upon the multiple modalities and genres through which many students already engage with fiction (video, online and/or fantasy role-playing games, horror, speculative and science fiction). With this approach, students in a seated class team up to create original alternative worlds in an online environment--including production of both digital and physical artifacts--within which their own (individual) stories are set. The result is movement between real and virtual space, as well as between shared creative acts and personal imaginative writing.