A spatial hierarchy consists of nested areas of different sizes. This concept is easy to illustrate with political areas. A state, for example, is part of a larger country, and at the same time it has smaller counties within it (and those counties may have cities within them, and neighborhoods within cities, and so on). The idea of a spatial hierarchy, however, can also be applied to watersheds, wholesale distribution areas, professional baseball "farm teams," and many other topics . . . (p. 186, see source for more)