Its rim sits flush with the present ground surface, and in wet weather it floods. The south-western end stone is so deeply buried that it can only be found by pushing something into the ground to feel for it. What exactly was placed inside, and by whom, is not known with any certainty.

The structure is a short cist, a form of burial container used widely in Ireland and Britain during the Early Bronze Age, roughly the second millennium BC. Typically a short cist consists of four or five stone slabs set on edge to form a small rectangular box, sealed with one or more cap stones, and used to inter a crouched or contracted body, sometimes accompanied by a decorated pottery vessel known as a Food Vessel or Beaker. The example at Lough Adoon fits that general description: its sides and ends are each a single slab, one cap stone remains loosely in place at the north-eastern end, and a second loose slab inside is probably another. Internally it measures 1.15 metres by 0.56 metres, and is roughly 0.4 metres deep. The floor, as far as investigation has shown, is covered with soil and rushes to a depth of about 25 centimetres, beneath which there appears to be a stony bottom. The resemblance to Early Bronze Age burial cists found elsewhere in Ireland is noted in J. Cuppage's 1986 archaeological survey of the Dingle Peninsula, though the classification remains uncertain. The valley setting is itself part of the deep geological history of the peninsula, the lough occupying a trough scoured out by glacial action through the central mountain ridge, leaving the surrounding ground saturated and largely unchanged.