Designing break-the-mold classrooms--learning spaces that depart dramatically from traditional classrooms--comes with increased risk, especially when the design will be replicated multiple times within a new building. One way to reduce risk is to build a life-size mock-up classroom before making final design decisions. This can help faculty better understand their needs, and help design teams avoid costly mistakes. In this article, the author describes a project he worked on a number of years ago at Harvard Business School (Massachusetts) that taught him how valuable this extra step can be. (Contains 8 photos.)