What remains on this rise in County Mayo is a semi-circular earthwork, roughly 29.7 metres across at its widest, with one clean straight edge where the quarry bit in and simply stopped the enclosure short. The rest of the site slopes gently in pasture, the surviving bank reduced to a low external scarp of around 0.4 metres, topped by a broad, shallow lip on the interior side.

A rath, in Irish usage, is a ringfort, typically a circular earthen enclosure that once defined a farmstead or defended residence, most commonly from the early medieval period. This particular example takes its name from the Irish 'Mullach Chairnn', meaning the Height or Hill of the Cairn, a name recorded in the Ordnance Survey Letters of 1838, compiled as part of the great nineteenth-century mapping of Ireland. Those same letters contain a vivid description of what the site once looked like: a ring of very large, rounded stones placed along the perimeter where the bank would have stood, enclosing a space roughly twenty-six yards in diameter, with the outer circuit measuring two hundred and forty-two feet around. By 1922, the OS map had already noted the quarry cutting into the eastern edge, and today not one of those large stones remains visible. The 1838 map shows a complete circular enclosure; the 1922 map shows the penannular form, open on one side, that visitors see now. The quarry pit itself drops roughly two metres below the level of the rath interior and extends forty-five to fifty metres to the north-north-east.

The setting gives some sense of why the location was chosen in the first place. The ridge commands extensive views north and east over low coastal grasslands, with Rathlacken Bay and Killala Bay visible beyond. To the south-west the land rises again to a further ridge. Whatever function the enclosure originally served, it was placed somewhere that could see, and be seen from, a considerable distance.