The outer wall, built in drystone and faced on both sides, has largely collapsed and grassed over, but its circuit remains legible in the landscape. A later field wall was laid directly on top of it across much of the arc, which is itself a kind of accidental preservation, the older structure absorbed into the working life of the land rather than quarried away. Inside, a series of radial walls subdivide the enclosure into fifteen or sixteen separate plots, and up to ten house sites can still be made out on the ground as low earthen platforms. Near the centre, a smaller square enclosure about 30 metres across contains a church and an earlier graveyard, the whole arrangement suggesting a self-contained community laid out with deliberate organisation.

What drew excavators here in the mid-twentieth century was precisely the absence of later interference. When archaeologist Duignan chose the site for excavation in 1950, and returned again in 1951 and 1953, he noted that there was no modern cemetery overlying the old one, no signs of medieval or later building, and that the original layout appeared to be unusually well preserved for a mainland monastery. That phrase, mainland monastery, is worth pausing over: early Irish monasteries of this type are far more commonly encountered on islands or coastal promontories, where isolation and difficult access helped protect them from later development. Kiltiernan's survival in ordinary farmland, relatively intact beneath its skin of grass and later walling, made it a rare case. Adding further complexity, the western sector of the enclosure contains a souterrain, an underground stone-lined passage of the kind typically associated with storage or refuge in early medieval Ireland, indicating that the community living within these walls had constructed features well below ground level as well as above it.