SUPPORT FOR CHILDREN'S EMERGING mathematical thinking is a characteristic of high-quality early childhood education. Young children's spatial thinking, an important component of mathematical thinking, is both innate and influenced by experience. Since spatial thinking contributes to children's mathematical thinking, it is important for children to engage in activities that support this learning. Early childhood educators are calling for guidance in how to support children's mathematical thinking in the context of an informal curriculum. In this paper, we describe how a project-based approach to mathematics teaching and learning provided a range of opportunities for children to investigate and rehearse understandings of two- and three-dimensional (2D and 3D) shapes and spatial thinking within the context of a project that was of ‘real world’ interest to the children. By intentionally embedding multiple opportunities for children to explore shapes and spatial thinking in a sequence of core learning experiences and complementary experiences, educators provided children with opportunities to rehearse shape and spatial concepts and related language in differing ways. Opportunities for formative assessment of children's learning are also discussed.