"The painter of the natives, Catlin, crossed the country for eight years and painted more than three thousand portraits (of them) wrote from this country on upper Missouri, 'Medicine is a mighty word in this land and it is necessary to understand it's meaning. The word Medicine means mystery and nothing else'." (3)
So you have to understand the traditional name of this bizar rocks. Suddenly you are standing in front of the rocks which were eroded into grotesque forms by wind. It becomes a holy place for the natives where the great mystery is present for all times.
Sioux and Cheyenne met here to celebrate different ceremonies. They were special close to the great mystery at places like this.