Its dimensions, roughly 17 metres north to south and 23 metres east to west, suggest it was once something more substantial, and the suspicion is that the substance was deliberately removed, carted away to fill in farm trackways, leaving behind only the depression and a scatter of material that pointed investigators towards what had once been there.

Fulachtaí fia are among the most common prehistoric monuments in Ireland, low horseshoe-shaped mounds typically found near water, formed from the heat-shattered stone that accumulated during repeated cycles of cooking or possibly other industrial processes involving heated water. They are ancient enough that their exact purpose is still debated, but their material signature, burnt and cracked stone, is distinctive. At Glantaunluskaha, that signature was identified in 1985 during the Castleisland District Archaeological Survey, which noted the presence of fulacht fia material within and around the subcircular depression and concluded that a monument of this type may have been quarried out, its burnt stone repurposed for practical nineteenth or twentieth century agricultural use. It is a fate that likely befell countless similar sites across Ireland, where ready-made aggregates were not always distinguished from ancient remains.

The hollow is still visible in aerial photography taken between 2011 and 2013, a faint but legible trace of something that was already half-erased by the time anyone recorded it formally.