Basic processes underlying spatial encoding and memory have ancient evolutionary origins and are shared by many neighboring branches of the phylogenetic tree. As a result, the study of spatial cognition and its neural correlates has been a fruitful area of research that has benefited immensely from making cross-species generalizations. Converging evidence from all areas of cognitive science – from the firing of single neurons in the rodent brain, to the development of spatial abilities in chicks, fish, and children, to visual scene perception in adult humans – reveals that environmental boundaries, such as walls, ledges, cliffs, hills, and other terrain-like structures, play a fundamental role in vertebrate spatial mapping and navigation behavior. The aim of this review is to bring together three decades of research in the first comprehensive boundary-based view of spatial cognition.