The structure at Lisnagregga is a cashel, an early medieval stone enclosure of the kind built across the west of Ireland as a farmstead boundary and place of protection, its walls thick enough to deter cattle raiders and opportunistic neighbours alike. This one measures roughly 26.8 metres in diameter, though you would have to know what you were looking for to read it as anything more than a low, irregular scatter of stone.

The site was noted by McCaffrey in 1952, catalogued as number 53 in a survey of the area, and the description has changed little since. The wall has long since fallen in on itself, leaving the cashel in a poorly preserved state. That collapse is not unusual for sites of this kind in Connacht, where centuries of agricultural clearance, land improvement, and simple neglect have reduced many comparable enclosures to faint earthworks or, as here, a tumble of undressed stone that blends quietly into the field boundary landscape around it.