The views up here are amazing. I would suspect that this may have been some kind of passage-grave at one stage. The view to the setting sun is fantastic over some low hills in cork and to the east is the sea around youghal.
I would think that the rising sun coming up out of the sea here would have been amazing. So if there was a passage perhaps it was aligned to a sun-rise. All just conjecture of course.
Also this cairn has great views into the mountains of Tipp/Waterford to the north.