What is missing is just as telling as what survives: there is no backstone closing the far end, and no roofstone overhead to complete the covering. The result is a structure caught mid-dissolution, its internal dimensions still measurable at roughly two and a half metres north to south and one and a half metres east to west, but open now to the sky it was built to resist.

Portal tombs, sometimes called dolmens, are among the oldest megalithic monuments in Ireland, typically dating to the Neolithic period. They consist of upright stones forming a chamber, usually capped by a large roofstone angled to give a distinctive raised-entrance profile. The Ardabrone example was catalogued by archaeologist Seán Ó Nualláin as part of his comprehensive survey of the megalithic tombs of County Sligo, published in 1989, which placed it within a broader pattern of such monuments distributed across this part of the west of Ireland. Sligo retains an unusually dense concentration of megalithic remains, from the passage tomb complex at Carrowmore to scattered portal and court tombs across the county's interior, and Ardabrone sits quietly within that wider prehistoric landscape.