It is not a ruin in any dramatic sense; more a boundary that has simply been waiting, held in place by the bog itself while the world above it changed. The structure measures roughly sixteen metres east to west, with a notably straight eastern side running twenty-two metres in length, and the whole thing is built in drystone, a technique relying on carefully fitted stones and no mortar. Most of the wall stands at only about sixty centimetres high and is partially collapsed, but the fact that it protrudes above the bog surface at all is part of what makes it legible after so long.

The enclosure sits within the remains of a broader field system, and the straight eastern wall has been absorbed into a relict boundary of that same system, suggesting the two were either contemporary or developed in close relation to one another. Large boulders are incorporated into the curving sections of the wall, which was common practice when builders worked around whatever the landscape offered rather than quarrying to a uniform specification. About ten metres to the west lies a hut site, which hints that this was once a working agricultural landscape, perhaps a small enclosed area associated with seasonal or permanent habitation. Bogs in Ireland have preserved many such sites by sealing them under accumulating layers of peat, and what survives at Erneen is essentially a slice of an early rural arrangement, its precise date uncertain but its function, organising land and sheltering some form of domestic life, reasonably clear from its form alone.