Whoever is responsible for these sites appears to have had more sophisticated astronomical knowledge and construction techniques than generally thought possible for the time.
This has lead to theories about help from either aliens or an advanced civilization such as Atlantis.
It is a circular mound with a stone passageway leading to chambers inside.
Lios Na Grainsi (or Fort of the Grange) is the largest stone circle in Ireland.
The circle is aligned with the rising sun of the summer solstice; the sun shines down directly into the centre of the circle. Locals apparently refuse to approach the site after sunset, since they believe that the circle returns to the Fey at this time.
But despite the fact that everybody has heard of Stonehenge, it’s worth reminding you with the help of the picture above just how incredible this site really is. It is unclear why, or even how the huge stones were erected as they were—creating an enduring mystery that has captivated people for centuries.
The most famous stone circle in the world, Stonehenge was constructed in phases between 15 B. In a not entirely unrelated side-note, some believe that the well-known rhyme, “eeny, meeny, miny, mo” may have its origins as an ancient counting system, possibly used by the same people who built Stonehenge.
A stone avenue, which leads out of the circle, points toward the setting midsummer full moon.
These days, we barely even watch the sun rise anymore—who can imagine what was going through the minds of these ancient builders when they saw the sun go down each night? It is the most intact Neolithic settlement in Europe, gaining it UNESCO World Heritage Site status and the nickname of “Scottish Pompeii”.The main passage of Cairn T is built so that the light of the rising sun on the spring equinox is narrowed into a thin shaft, illuminating the art within.Cairn S is aligned to the cross quarter days, and it is believed that Cairn V (of which there is very little remaining) indicated the winter solstice. Not much remains of the original stones, but what does remain hints that this must have been a magnificent sight indeed.The main passage is aligned so that the rising sun of the winter solstice floods the interior with light, which enters through an opening above the doorway.Once again, archeologists do not completely understand the original purpose of Newgrange, but most agree that it was probably used in religious rituals.The site is aligned to the summer solstice, and it has been argued that year-round alignments would have allowed Bryn Celli Ddu to be used as an agricultural calendar.