The wall is modest in scale, at least thirteen and a half metres long and no more than half a metre high, running east to west across ground that was once, before the bog grew over it, an organised agricultural landscape. It came back into view only because of turf-cutting, the traditional harvesting of peat for fuel, and even now several of the boulders remain partly covered by the peat that buried them.

What makes this wall quietly remarkable is its age relative to the bog itself. Pre-bog field walls are structures that predate the formation of the surrounding peat, meaning they were built and in use before waterlogged conditions caused the bog to develop and slowly engulf them. In the west of Ireland, this process often began in the Neolithic or Bronze Age, when farming communities were clearing and dividing land that would later become the blanket bog we see today. The wall at Mweelin is a trace of that earlier, drier world, a boundary drawn by people who had no reason to expect the land would eventually swallow their work. Roughly thirty metres to the south-east, on the opposite bank of the river, there is a separate enclosure that may have been part of the same agricultural arrangement, though the relationship between the two structures remains uncertain. The wall was first brought to wider notice by Helen Riekstiņš.