This is a cashel, the Irish term for a ringfort defined by a stone wall rather than an earthen bank and ditch. The one at Poulanine is suboval in plan, modest in scale, with internal dimensions of roughly 17.6 metres north to south and 15.7 metres east to west. Its defining wall, around two metres wide, still shows its outer face almost all the way round, though it survives to only a modest height.

What makes the site quietly interesting is its context. It sits within what surveyors classify as a multiperiod field system, meaning the surrounding land has been divided, managed, and reworked across successive eras, leaving overlapping traces in the ground. The cashel itself was already being mapped in the mid-nineteenth century, appearing on both the 1842 and 1920 editions of the Ordnance Survey six-inch map, marked with hachures, the fine radiating lines cartographers used to indicate an enclosing bank or wall. A later drystone wall, built north to south at roughly 0.6 metres wide and about a metre high, has been laid directly over the cashel and may have disturbed the eastern perimeter. That kind of intrusion is common across Irish early medieval sites, where later agricultural boundaries were drawn without regard for what lay beneath. More striking is the density of remains nearby: a separate enclosure sits around 60 metres to the south-south-east, and a structure recorded under the name Caherlisnanroum lies roughly 104 metres to the south, suggesting this was once a well-settled and carefully organised stretch of ground.