Three key features of a proposed capstone mathematics course for the preparation of teachers at the secondary level are: 1) teacher candidates examine concepts from the curriculum at a deeper level in the context of rich problems; 2) they investigate common themes in the math curriculum, such as shape and change, then collaborate on and present their research; and 3) they create portfolios of extensions and course reflections, products that require them to engage in higher-level, original thinking. Through this variety of assessments, the instructor is able to see future teachers of mathematics from multiple perspectives: their mathematical knowledge, their dispositions, and their beliefs about what mathematics is and how to effectively communicate the essential ideas. Participants' reflections indicate that those aspects of the course that have the greatest value for improving teaching are collaboration, problem solving, conceptual learning, and opportunities for exploration.