It is 36 metres long and about a metre wide, running from one peat-face to another, and it pre-dates the bog itself. That last detail is the quietly remarkable thing: the wall was built on open land, and then the bog grew over it, swallowing it whole until turf-cutting brought it back into view.

Pre-bog walls are structures that were constructed before blanket peat began to accumulate in an area, a process that in many parts of Ireland started several thousand years ago as the climate became wetter and soils became waterlogged. They are physical evidence that landscapes now given over entirely to bog were once farmed, divided, and managed by people whose settlements have otherwise left little trace. This particular wall lies near the edge of a large boggy tract, roughly 270 metres north-east of Lough Cummernamuck. The peat around it has been cut down to about half a metre below the top of the wall, which is how the structure became visible at all. Its drystone construction, stones laid without mortar and relying on their own weight and fit to hold together, suggests it served as a field boundary, dividing ground that was once workable enough to be worth enclosing.