The standard modern maps, in which a kilometer is a kilometer no
matter what the terrain or body of water, are therefore profoundly misleading
in this respect. Settlements that may be three hundred or four hundred kilometers
distant over calm, navigable water are far more likely to be linked by
social, economic, and cultural ties than settlements a mere thirty kilometers
away over rugged, mountainous terrain. In the same fashion, a large plain
that is easily traversed is far more likely to form a coherent cultural and social
whole than a small mountainous zone where travel is slow and difficult