Polar circle
A polar circle is either the Arctic Circle or the Antarctic Circle. On Earth, the Arctic Circle is at a latitude of 66˚ 33' 38" N, and the Antarctic Circle is at a latitude of 66˚ 33' 38" S. Areas between each polar circle and its pole (North Pole, or South Pole) will each year have at least one 24 hour period when the sun is continuously above the horizon and at least one 24 hour period when the sun is continuously below the horizon.