The cashel at Ballynacarragh is a different proposition. Sitting at the western end of a ridge in undulating pasture in County Mayo, it layers defence upon defence in a way that speaks of deliberate, considered effort rather than a simple enclosure for livestock or a modest farmstead.

A cashel is a ringfort whose primary enclosing wall is built of stone rather than earth, and here that wall stands 2.2 metres high and 2.5 metres thick, forming a roughly circular space measuring about 32.5 metres north to south and 31 metres east to west. But the stone wall is only the beginning. Inside it sits an earthen bank, scarped steeply on its outer face, and beyond the wall lies a fosse, a defensive ditch, dropping to a depth of 3.3 metres. Beyond that again runs an outer earthen bank, whose circumference traces roughly 202 metres and whose external height reaches around 10 metres on its more dramatic faces, descending in steep terracing from the south-southeast round to the northwest before dropping back to ground level. The single entrance, on the east-southeast, is reached by a causeway 4.4 metres wide that bridges the fosse, the only break in that concentric ring of earthwork and stone. The combination of a mortared or dry-stone cashel wall with an inner bank, a deep fosse, and an outer bank of this scale is relatively unusual, and suggests that whoever occupied or commissioned this site wanted something considerably more formidable than a standard enclosure.