Spread across rough, rocky pastureland, a roughly circular cashel, a type of early medieval stone-walled enclosure, has collapsed so thoroughly that all that remains is a low, rubble spread somewhere between three and five metres wide and no more than sixty centimetres high at its tallest. There are no facing-stones left to speak of, no discernible original entrance, and the whole thing is buried entirely under briar and thorn. A later field wall cuts straight across its northern edge, indifferent to whatever came before it.

The site was already being mapped by the early twentieth century, appearing on the 1915 edition of the six-inch Ordnance Survey map, though later records classified it cautiously as a mere enclosure before its cashel character was acknowledged. A souterrain, an underground passage or chamber typically associated with early medieval settlement and used for storage or refuge, was marked on Tim Robinson's 1977 map of the area, but a field inspection in 1997 found no trace of it whatsoever. It may have been consumed by the same collapse that obscured everything else, or the original identification may simply have been mistaken. To the east of the cashel, a subrectangular enclosure once abutted the main site; by the time of the 1997 inspection it had been cleared, and some of its stones appear to have been dumped directly onto the cashel's already battered wall-line. Archaeologists have suggested this enclosure may have functioned as an annexe contemporary with the cashel itself.

What gives Poulbaun its quietly strange quality is not any single feature but the density of remains in the surrounding landscape. Two further cashels sit 115 metres and 260 metres to the south-south-west, and another enclosure lies 125 metres to the north-west. The site at Poulbaun is the most degraded of this cluster, stripped of legibility by time, agricultural reworking, and thorny overgrowth, yet its position within what appears to have been a concentrated early medieval settlement pattern makes even its rubble worth pausing over.