The circle design is an archetypal symbol of power and universality.  This Celtic circle design of an endless knot contains 12 outer rings, 6 middle rings, and 3 center rings, all multiples of three--the archetypal number of trinities.  The center is a triangular runic cross that divides the circle into 3 groups of 4 rings.  The Trinitarian formula with the fourth element is also a universal spiritual symbol. Complex designs like this were designed to teach the Celts that they were connected to the entire universe and their lives were purposeful.