This large henge (embanked enclosure) located beside the River Boyne at Brugh na Bóinne, known on archaeological maps simply as Site P, has been identified tentatively by archaeologist Geraldine Stout as the site referred to in ancient lore as Caisel nOengussa, the Cashel of Oengus.
A description of sixteen sites at the Brug na Bóinne complex is described in the Dindshenchas, a collection of middle Irish legends from around AD900-1200 that poetically describe the "lore of thelandmarks".
Because of its somewhat denuded nature, Site P is best seen when the sun is low in the sky, as demonstrated by this photo taken at 7am this morning on a beautiful spring dawn. Behind the henge to the upper left is a double pond, often described as a figure-of-eight pond, which is thought might be a manmade feature. Caiseal Oengusa and the double pond attract whooper swans, which spend some of their time at these locations when they come to the Boyne Valley from Iceland to spend the winter here. Further off in the distance, behind the double pond, is Mound B, on the flood plain of the Boyne.