The Antarctic Circle is one of the five major circles of latitude, located at approximately 66.5 degrees south of the equator. It marks the northernmost point where, during the summer solstice, the sun remains above the horizon for a full 24 hours. This phenomenon is known as the "midnight sun," and it occurs in regions south of the Antarctic Circle. In contrast, during the winter solstice, areas within the Antarctic Circle experience polar night, where the sun does not rise above the horizon for an extended period. This unique climate affects the ecosystems and wildlife, including species like penguins and seals, that thrive in the harsh conditions of the Antarctic region.