Cycles of the cosmos inscribed in the great passage tombs of Brú na Bóinne: a calendrical framework for regional gatherings, religious festivals and monumental construction

The alignment of Newgrange’s ‘virtual axis’ to the winter solstice sunrise and summer solstice sunset, and the possible alignment of Knowth’s eastern tomb passage to a ‘perceived-equinox’ sunrise, as its Neolithic builders understood it to be, are likely to reflect an annual festive ‘calendar’ of gatherings and ceremonial events at Brú na Bóinne during the Middle to Late Neolithic period and possibly the Chalcolithic and Early Bronze Age too. The megalithic art adorning the entrance stone to Newgrange was an integral part of ceremonies related to the winter solstice sunrise, while the highly decorated kerbstones 52 and 67 to the rear of Newgrange are likely to be related to summer solstice events.
In addition to key architectural details of the eastern tomb passage of Knowth, some aspects of the megalithic art and related features external to the eastern and western tomb passage entrances seem to accord with the possibility of equinox-related ritual and ceremony at this site. If this is the case, then the apparent lunar significance of the megalithic art on Knowth’s Kerbstone 52 is afforded an additional significance. This hypothesis also proposes that ceremonies associated with autumnal equinox events at Knowth were likely to have been coupled with the coordination of regional gatherings and the possible transportation of megalithic stones and other monumental building materials upriver as far as the bend of the Boyne.