Antarctic Circle

The Antarctic Circle, the southernmost of Earth's five main latitude circles, delineates the Antarctic region to its south and the Southern Temperate Zone to its north. Here, the Sun remains above the horizon for an entire 24-hour period at least once annually (hence visible at midnight), and its center stays below the horizon for a full day or more each year (thus not visible at noon). The Arctic Circle, its northern counterpart, exhibits the same phenomena.