The name given to it, Dermot and Grania's Bed, belongs to a whole category of megalithic monuments scattered across Ireland, each one supposedly a resting place used by the eloping lovers Diarmuid and Gráinne during their long flight from the ageing king Finn Mac Cumhaill. The folk tradition attached itself so persistently to ancient monuments that the phrase effectively became a generic term for any conspicuous prehistoric structure whose true origins had been forgotten. Here, the real story is considerably older than any medieval romance.

The monument is a roughly circular cairn, a large mound of stone approximately thirty metres in diameter and two metres high, with a small polygonal chamber near its centre aligned roughly east to west. A cairn of this type, covering an internal stone-lined chamber, is characteristic of a passage tomb, a form of Neolithic burial monument constructed in Ireland from around 3500 BC onwards. The chamber here is modest, its internal length just over two metres and its width around one metre, with sidestones ranging in height from 1.2 to 1.8 metres. It was documented and described in detail by Ruaidhrí de Valera and Seán Ó Nualláin in their Survey of the Megalithic Tombs of Ireland, published in 1982. The site does not stand entirely alone in the landscape; roughly nine kilometres to the south-south-east, on Temple Hill at the western end of the Galty mountains, another cairn is visible, possibly also a passage tomb, suggesting this part of Tipperary was a meaningful location for prehistoric communities.

Forestry has pressed close to the monument on three sides, coming to within ten metres on the north, east, and west, though felling to the west has opened up a clear view across the Galty mountains and their foothills. A stone wall runs east to west along the southern edge of the mound. The cairn itself remains thickly vegetated, which obscures the stonework but also, in its own way, preserves something of the atmosphere of a structure that has been quietly accumulating moss and legend in equal measure for several thousand years.