Sites A and B at Newgrange
Sites A and B are two of the forty or so satellite monuments which surround Boyne Valley. Satellite mounds are a common feature of this type of monument, where smaller mounds are built around a larger and probably later monument.
The best example is Knowth, which has 18 smaller mounds encircling the main monument. The Carrowmore complex in County Sligo had almost 40 satellites around the main monument at Listoghil.
Sites A and B in the Boyne Valley are both located on the floodplain near the river below Newgrange. Site A is a large mound, about 23 meters in diameter, which has never been excavated or opened. The mound is encircled by an enclosing bank measuring 100 meters in diameter, which is now mostly ploughed out. Faint traces of the enclosure can be seen in the picture above.
The mound is not in the centre, but offset to one side. Enclosing banks seem to have been a common enough feature of passage graves. They also survive at the Giant's Ring in County Down, Site 1 at Knocknarea and Muckelty Hill in County Sligo, Croughan cairn in County Donegal, and Eochy's Cairn north of Cong in County Mayo.
Site B, another satellite of Newgrange is right on the banks of the Boyne. The mound is about 20 meters in diameter and has never been opened. One of the interesting things I have found about the Newgrange satellites is that they all fall on the arcs of circles drawn using Knowth and Dowth as centres, which would suggest that Newgrange was the last of the three mounds to be built.