In both traditional and modern mythology, from the Iliad to Twin Peaks, an unbroken circle is a symbol of unity, purity, and eternity. It is generally associated (in dualistic morality plays) with the good guys.

It appears often in heraldry (most notably in the form of the Roman wreath - the circular bundle of sticks that give fascism its name).

In the legend of camelot, the table of King Arthur and his knights is an unbroken circle. The halo of angels and other judeo-christian blessed beings is traditionally circular. In Blade Runner, the unbroken circle of the human (or replicant) eye is a recurring motif. The list goes on and on...