The polar circle (66° 33' of latitude) marks the limit of the area where the midnight sun can be observed i.e where the sun does not set but only comes close to the horizon around midnight on the day of the summer solstice. Depending on the latitude, the axis of the sun's trajectory is more or less inclined from the horizontal plane. At the north pole (90° of latitude), the height of the sun varies between 0° and 23° during the 6 months of the spring-summer period, its trajectory draws a complete circle parallel to the horizontal plane and it never sets.