The enclosure at Glencolumbkille is the kind of site that rewards close attention, not because it is dramatically preserved, but because so little of it remains, and what does remain asks questions that are not easily answered. An ecclesiastical enclosure is broadly what it sounds like: a defined precinct, usually of early medieval origin, marking out sacred ground around a church or monastic foundation. Here, the outline survives only in fragments, and reading the landscape takes a little patience.

T. J. Westropp, writing in 1913, found an enclosure he described as a large, low ring-fort of earth and stones, much reduced even then. Around the northern arc ran a bank up to 1.83 metres high and roughly three metres wide, faced in part with large stones; the south side was defined more by dry-stonework walling. The northwest and southeast edges were terraced up to about 1.22 metres. By the time of a recorded visit in 1982, these features had been substantially reduced further, and an inspection in 1999 confirmed what the intervening decades had done. By then the enclosure, roughly 99 metres east to west and 83 metres north to south, survived at its clearest along the west-northwest arc as a low bank of stone, gravel and earth, standing no more than a metre on its outer face. Elsewhere the perimeter had faded to a barely traceable scarp. A row of large boulders, 28 metres long, had been deposited along the eastern edge, and later rubble had been tipped onto the bank at the west-southwest. A field wall running from north-northwest to north-northeast overlies or sits just inside the original line, quietly obscuring the very boundary it shadows.

Inside the enclosure, a church sits in the southern centre, occupying the northwest corner of a graveyard. Just outside the graveyard's eastern side, a broad curvilinear scarp about a metre high hints at earlier organisation of the ground. Perhaps most evocative is a wayside cross about 90 metres to the northeast, placed at the point where a trackway from the church once met the main road, a small marker of the routes people once walked to reach this place.