Everybody recognizes what is it… or, rather, where is it located. But, do we really know _what_ is it (by its function), really?
Not far from Stonehenge, to the North, there is another, less famous, but larger Avebury Stone Circle. And it’s not only a Circle, there is an alley of stones, like in Carnac, leading to the Circle itself.
Of course there are plenty of hypotheses about what Stonehendge and similar Stone Circles were built for. The most popular is that it was a giant calendar, marking special dates like Solstices and Equinoxes for cultic purposes of Druids and their Neolithic predecessors. Contemporary Druids, whom, barefoot, one can always find in vicinities of the Circles, touching and hugging Stones, fuel this hypotesis, conducting festivals on these special days.
Nevertheless the question of meaning of the obvious Sun veneration by ancient Celts, as well as indo-europeans in general, remains. Indo-europeists of ninetieth century, for example, Max Muller, brought fourth so called meteorological theory, that all indo-european myths are just a retelling of the daily/monthly/yearly solunar cycles. That explanation worked fine for particular mysts, but on the whole corpus of folklore it collapsed under weight of mutual contradictions.
For example the Sun is simultaneously symbol of two completely different divinities – Mithra, who is a symbol of Justice, and the Sun is his All-Seeing-Eye; and Ashvin twins, who are patrons of fertility and agriculture, and the Sun is a live-giving torch in their sky chariot.
In twentieth century the meteorological theory gave the way to another explanation – all these celestial analogies are just hyperbolic, picturesque illustration of the higher abstract ideas of fairness, justice, honor, bravery, creativity and fertility.
The actual function of the Stone Circles may be betrayed by Stonehenge’s another, and older name – Choir-gaur, or Giant’s Carol. Etymology of the word Carol/Choir/Хор and words for circular dances on other indo-european languages is traced (as usual) to the Latin and then Greek words choraules/χορός, and then goes back to proto-indo-european root *gher- “to grasp/enclose”. Such indo-european circular dances acompanied by singing had a magic functionality related to birth and resurrection, and later were adopted by Christian Church, and, by decisions of councils in sixth century, were stripped of their dancing component, which resulted into emergence of a well known contemporary tradition of Christmas Carols.
This birth/resurrection atributes are closely related to function of the third divine indo-european caste of Ashwin/Dioscuri twins and their mascot – the Horse. Etymology of the word horse is obscure and, as usual in such cases, has many competing hypotheses, one of which is the name of Slavo-Iranian deity Hors, which literally means “bright Sun”.