The enclosure is substantial, measuring roughly 52 metres across from north to south and 56 metres from east to west, ringed by a well-defined earthen bank that rises between one and 1.8 metres on its exterior face. That scale places it in the same broad category as a ringfort, the circular enclosed settlements that dot the Irish countryside in their thousands, though the cartographic designation here points to a very different kind of use in more recent memory.

Sites like this one were known in Irish as cillíní, informal burial grounds used for the interment of unbaptised children, as well as strangers, suicides, and others excluded from consecrated ground by ecclesiastical convention. The practice persisted in rural Ireland well into the twentieth century, and it was common to repurpose older, already-enclosed earthworks for this purpose, their ancient boundaries lending a kind of liminal sanctity. At Kilgarvan, the interior sits at roughly the same level as the surrounding land, and three breaks in the bank have been recorded, two in the north measuring around four metres wide and one to the southwest at approximately three metres. In the northwest sector of the interior, several large blocks of stone have been noted, though it is unclear whether these remain in their original positions. The relationship between the earthen enclosure itself and its later use as a burial ground is not firmly established, leaving open the question of what the site was first built to contain or protect.