The Circle and the Wheel and the Sundoor

Four coiled rattlesnakes surrounded by Black Endless Snake in a Beautyway sandpainting represent the time of day: dawn, noon, sunset and night and they guard the healing, fertilizing power of water represented by Black Endless Snake. Since snakes can go below the earth's surface, they know the location of wells and springs and can bring rain.
Since the circle has been a recurrent image for the center from which creation takes place, it is not then surprising that it has also been a universal symbol of the female through aeons of time in human cultures. Its power as a symbol of the female is not just because it is a visual analogy to the womb or the vaginal canal, but more importantly because the female is the unmanifest, the potential for new life; and no creation takes place until the empty circle is impregnated.
I am using the word female because I want to keep our thinking on the biological level. One of the things that happens in our culture today is that not only men make projections on the female, but women also make projections on the female too, and we are, historically, in the midst of a time when we are trying to sort out those projections to see their meaning and content.