User-created virtual worlds are emerging technologies with rapidly growing acceptance in education. Of the various reported educational uses of these virtual worlds, the focus of this chapter is on virtual worlds for constructivist learning activities, because this use has application to many real-life courses and has the potential to transform teaching and learning. To assist educators with recognizing and understanding virtual world learning activities, Antonacci & Modaress (2005, 2008) developed the Interaction-Combinations Integration model. However, this model has not been studied in actual virtual-world learning practice. Using a case study method, this chapter examines the usefulness of this model to organize and describe actual virtual world learning activities, provides additional learning activity examples, and describes what was needed to implement and conduct these learning activities.