You have heard that everything an Indian does is in a circle , and that is because the power of the world always works in circles , and everything tries to be round. In the old days when we were a strong and happy people , all our power came to us from the Sacred Hoop of the nation and so long as the Hoop was unbroken the people flourished.
The flowering tree was the living center of the Hoop , and the circle of the four quarters nourished it .....The East gave peace and light , the South gave warmth , the West gave rain , and the North with its cold and mighty wind gave strength and endurance.
This knowledge came to us from the outer world with our religion. Everything the Power of the World does is done in a circle....the sky is round and I have heard that the earth is round like a ball and so are all the stars.....the wind , in its greatest power , whirls....birds make their nests in circles , for theirs is the same religion as ours .
The sun comes forth and goes down again in a circle....the moon does the same , and both are round.
Even the seasons form a great circle in their changing , and always come back again to where they were . The life of a man is a circle from childhood to childhood and so it is in everything where power moves.....
Our tipis were round like the nests of birds and these were always set in a circle , the nation's Hoop.....a nest of many nests where the Great Spirit meant for us to hatch our children.

Passage taken from the autobiography of Black Elk