In this article, the author reports findings from a project designed to explore approaches for improving students' mathematical learning outcomes in relation to the base ten number system. The project explored the role of a commonly used teaching activity, referred to in the project as the "base ten game," in developing children's understanding of the number system. The game involves students using a place value board and concrete materials to develop an understanding of the structure of the number system and to learn to operate on numbers using this structure. This project revealed the necessity of explicitly developing links between the concrete materials, the learning activities, and the structure of the number system to support the development of relational understanding of place-value. (Contains 3 figures.)