Here in Farranyharpy, in county Sligo, that depression traces the buried line of a souterrain, an underground passage or chamber typically cut into the earth and lined with stone, most commonly associated with early medieval settlement. The entrance to it survives, set into the inner face of the cashel wall in the south-west quadrant, and it remains the most legible feature of a monument that has otherwise fared poorly over the centuries.

The site is a cashel, a type of ringfort defined by a stone enclosing wall rather than the earthen banks more commonly associated with the form. It sits towards the south-western end of a north-east to south-west ridge, with steep drops to the south-east and west, and a gentler slope opening to the east. Red Hill overlooks it from that direction. The wall that once enclosed the oval interior, measuring roughly 29 metres north to south and 18.5 metres east to west, now survives only as a degraded remnant, standing no higher than 1.4 metres at its most substantial point on the western side and dropping to around half a metre on the east. The ground within is uneven and scattered with sod-covered stones, the collapsed remains of what the enclosure once comprised. A second enclosure sits immediately to the east, suggesting this was not an isolated structure but part of a small cluster of related features set into sharply undulating pasture.