North of the Arctic Circle, there is midnight sun during the summer and twilight during the winter. In simple terms, the Arctic Circle therefore represents the edge of the Arctic.

The Arctic Circle in the north and the Antarctic Circle in the south are the theoretical limits of the midnight sun and twilight months. North of the Arctic Circle, the sun is below the horizon 24 hours a day for a period during the winter, and above the horizon 24 hours a day during the summer.

The Arctic Circle we can see on a map follows an imaginary line along the mean value of the Earth’s tilt, i.e. 23 degrees 27′, and consequently on 66°33’42.5″. The best-known marker can be found 650 m (2130 ft) above sea level on Saltfjellet, the extensive mountain massif in the centre of the county of Nordland.