A cashel is a stone-walled ringfort, the kind of enclosed farmstead that once dotted the Irish countryside in their thousands, but this one is unusual for its scale. Its roughly circular enclosure measures nearly fifty metres across internally, the double-faced wall built from the thin, coarse limestone slabs that the Burren yields so readily, and laid directly onto karst pavement, the bare fractured limestone bedrock that sits just beneath the thin grass here. The wall has been reduced to its footings over the centuries, standing no more than about eighty centimetres on the exterior face, but the outline remains clear, the interior slightly concave within it.

The antiquarian Thomas Westropp recorded the site in 1917, noting the character of the stonework and the degree to which it had already been robbed down. His observation still holds. The entrance, positioned at the north-west, is a narrow passage barely a metre wide internally, flanked on each side by two large stones, with a single upright stone standing at the south side of the exterior opening. That upright, just over a metre tall, is one of the more arresting details, quietly marking a threshold that has not functioned as one for perhaps a thousand years. Inside, west of centre, are the remains of a small subrectangular hut, and a later drystone wall, probably agricultural in date, has been built directly over the outer face of the cashel wall running from north-west around to the south. The cashel sits within a multiperiod field system, meaning the landscape around it carries traces of use from several different eras layered one over another.

The site does not stand in isolation. A cairn lies roughly twenty metres to the east-south-east, a second enclosure about fifty-eight metres to the south-south-west, and another cashel around a hundred and sixty metres to the south-east. The plateau at Poulanine holds, in other words, a concentration of early activity that makes the ground itself feel accumulated rather than empty. Both the 1842 and 1920 editions of the Ordnance Survey six-inch maps marked the cashel with hachuring, the conventional cartographic symbol for earthworks, suggesting it was already a recognised feature of the landscape long before anyone thought to measure it precisely.