Known on Ordnance Survey maps as Cahercarbery More, its Irish name, Cathair Cairbre mór, translates roughly as the great stone fort of Cairbre, a personal name that anchors the site, however loosely, to a specific individual from an otherwise unrecorded past. A promontory fort is a type of enclosure that uses natural coastal geography, cliffs or headland edges, as part of its defences, supplementing the drop of the land with constructed banks and ditches on the landward side.

Cahercarbery More is defined by three earthen and stone banks, the inner two built from stone rather than piled earth, with two fosses, or defensive ditches, cut between them. A causeway enters the interior from the east, suggesting a deliberately controlled point of access. The internal diameter east to west measures 80 metres, with an external diameter of 95 metres, and the stone wall itself extends for approximately 90 metres. Within the shelter of the inner wall, traces of small hut sites have been identified, hinting at a community that once lived and worked within the enclosure rather than merely retreating to it in times of threat. Roughly half a mile to the south lies a companion site, Cahercarbery Beg, the lesser fort of Cairbre, suggesting this stretch of coastline was once a place of some significance, with two substantial fortified enclosures occupying the same short run of headland.