This is the parallel of latitude that runs 66° 33' 38" south of the equator. Within the Antarctic Circle, the Sun is above the horizon for, at least, 24 continuous hours per year, in conjunction with the summer solstice. Likewise, in conjunction with the Antarctic winter solstice, the sun is below the horizon for, at least, 24 continuous hours.
The continent of Antarctica forms a land mass covering much of the area within the Antarctic Circle.
See also: Arctic Circle