It runs for roughly 70 metres, stands between half a metre and a metre and a half high, and was built in a deliberate two-layer method: large stones, each up to 90 centimetres long, laid end to end as a foundation course, with smaller stones placed on top. What makes it quietly puzzling is that no one is entirely certain what it is for, or when it was built.

The wall's relationship with the landscape around it raises more questions than it resolves. Along its eastern stretch it sits on beach sand; towards the west, it rests on marine clay. Whether it continues beneath the peat banks that line the shore remains unclear, which means its age cannot be pinned down with confidence. One plausible reading is that it is relatively recent, built as a practical measure against coastal erosion rather than as a conventional field boundary in the agricultural sense. That reading gains some weight from the condition of its north-western end, where a 9.5-metre section is buried under heaps of builders' rubble, apparently a later attempt to shore up and reinforce what was already there. Two further walls sit close by, one roughly ten metres to the east and another ten metres to the north, suggesting that whatever effort was made to hold this shoreline, it was repeated more than once.

The wall's arc mirrors the curve of the peat banks themselves, which gives it an almost deliberate elegance despite its uncertain origins. Drystone construction, in which stones are fitted together without mortar and rely on weight and placement alone for stability, is common across the west of Ireland, but walls built specifically to resist the sea rather than to divide land are less frequently documented. At Poll Raithní, the distinction between the two purposes may never have been entirely clear to the people who built it.