The term megalithic covers a broad family of prehistoric monuments built using large stones, including portal tombs, wedge tombs, court cairns, and passage graves, all of which appear across the west of Ireland and broadly date to the Neolithic and early Bronze Age periods, roughly four to six thousand years ago. What kind of structure occupies this particular patch of Mayo ground remains, for now, a matter for the archive rather than the open record.

Mayo is one of the more densely monument-scattered counties in Ireland, its boglands and hillsides having preserved prehistoric remains that elsewhere were lost to intensive agriculture or development. Ballyheer, like many Mayo townlands, carries its history quietly, its name derived from the Irish and layered over a landscape that was already ancient when early medieval farmers first gave it a name. Without further detail currently in the public domain, the specifics of this structure, its form, its dimensions, its state of preservation, remain undisclosed.