Linked from
The 11 pages that link to Solstice, each with the reason it gives.
Axial tiltRelated: Solstices mark the strongest seasonal effects of axial tilt.
Celestial equatorRelated: The Sun’s declination reaches its yearly extremes relative to this circle.
Antarctic CircleRelated: The solstices bring the longest daylight and darkness at the circle.
Solar calendarRelated: Solstices mark seasonal turning points used to define some solar years.
Winter solsticeNarrower topic: The winter solstice is one of the two seasonal solstices.