To some indigenous peoples of North America, the medicine wheel is a metaphor for a variety of spiritual concepts. A medicine wheel may also be a stone monument that illustrates this metaphor. Historically, most medicine wheels follow the basic pattern of having a center of stone, and surrounding that is an outer ring of stones with "spokes" (lines of rocks) radiating from the center to the cardinal directions (east, south, west, and north). These stone structures may be called "medicine wheels" by the nation which built them, or more specific terms in that nation's language. Physical medicine wheels made of stone were constructed by several different indigenous peoples in North America, especially the Plains Indians. They are associated with religious ceremonies. As a metaphor, they may…