Synchronous collaborative (“multi-user”) computer-aided design (CAD) is a current topic of academic and industry interest due to its potential to reduce design lead times and improve design quality through enhanced collaboration. Minecraft, a popular multiplayer online game in which players can use blocks to design structures, is of academic interest as a natural experiment in a collaborative 3D design of very complex structures. Virtual teams of up to 40 simultaneous designers have created city-scale models with total design times in the thousands of hours. Using observation and a survey of Minecraft users, we offer insights into how virtual design teams might effectively build, communicate, and manage projects in a multi-user CAD design environment. The results suggest that multi-user CAD will be useful and practical in an engineering setting with several simultaneous contributors. We also discuss the effects of multi-user CAD on team organization, planning, design concurrency, communication, and mentoring.