When planning the most efficient route from one location to another, people tend to prefer southern routes overnorthern routes of equal length and complexity. This asymmetry has been attributed to implicit associations between cardinaldirection and relative elevation (i.e., north = higher), and holds even when regional topography conflicts with these associations.No such asymmetry has been observed between eastern and western routes. Here we provide evidence for an eastern-westernasymmetry in participants residing in an environment with east-west topography differences. Residents of Colorado Springs,CO, where topography is mountainous to the west, showed a reliable preference for eastern routes over equal-length westernroutes on a Colorado Springs map, but not an unfamiliar map. This pattern held even though the represented areas contain min-imal elevation differences. Our findings suggest that regional topography can induce a novel, physically unfounded asymmetryin otherwise unbiased representations of the spatial environment.