(Medicine Wheel in Adamsville Cemetery, Arizona)
In Arizona, you run into medicine wheels from time to time and especially at the vortexes in Sedona. They are beautiful, but they are also symbolic. Two things I've always dreamed of having in a garden are a labyrinth and a medicine wheel. Here's a chart to show you the quadrants of a medicine wheel:
Some who construct them, use rocks for the cross pieces in the color of the direction, like yellow rocks pointing to the eastern quadrant, et cetera.
These are a grounded and sacred place to interact with the spirit world. Some stand in the during the season facing the appropriate direction. It means something different to each culture and even to the new agers and wiccans who have borrowed the concept for their own process. Everyone has a different experience, but for most it is a way of staying focused, a kind of spiritual reset button.
Here is a wonderful site that explains how to construct your own.