In Newgrange, just north of the River Boyne in County Meath, Ireland, there exists a giant burial tomb, constructed, it is estimated, around 3200 BC and measuring over an acre in area .  Little is known about the people who built it.  However, we can surmise that they had some knowledge of both astronomy and engineering since each year, only at dawn on this day, the Winter Solstice, a beam of sunlight shines through a specially contrived opening above the tomb entrance, illuminating carvings on the walls of an inner chamber.