The walls are pre-bog, meaning they were built before the bog grew up and swallowed them, which places their origin in a period when this landscape looked nothing like it does today. Turf-cutting, the traditional practice of harvesting peat as fuel, has been slowly exposing them, returning to visibility something that had been sealed underground for centuries, possibly millennia.

The two uncovered lengths appear to form adjacent sides of a roughly rectangular structure, its long axis running northeast to southwest and measuring more than seventeen metres in length and over thirteen metres in width. The walls are built of large slabs, a construction method associated with field systems that predate the formation of the bog itself. Blanket and raised bogs in the west of Ireland have long been known to preserve earlier agricultural landscapes beneath them, and field boundaries of this kind, sometimes associated with Bronze Age or Neolithic farming activity, have been documented elsewhere across Connacht. The exact date of the Crocknaraw walls is not recorded, but the context alone, buried under accumulating peat on what was once open, workable ground, suggests considerable age. What remains visible is only a partial picture; the other sides of the enclosure, if they survive at all, likely lie beneath the surrounding bog.