The rath at Clashnagarrane has been levelled to the point where it survives only as a concave depression roughly thirty metres across, sitting at the lip of a steep east-facing slope. Below it, the ground falls away sharply to the river valley floor, a position that would have given whoever lived here a commanding view of the landscape and, presumably, of anyone approaching from the east.

A rath, the Irish term for a ringfort, was typically a circular earthen enclosure, defined by one or more banks and ditches, used as a farmstead during the early medieval period, roughly between the fifth and twelfth centuries. Though this one has lost most of its physical fabric, it was clearly substantial in its time. When surveyors recorded it in the 1840s for the Ordnance Survey Name Books, they described it as a large rath in the south-eastern end of the Kilcummin townland. The 1846 Ordnance Survey six-inch map shows it as a roughly circular enclosure of around forty metres in diameter, with field boundaries pressing in on the north, south, and west arcs, which likely accelerated the gradual erosion of the earthworks over time. Beneath the surface, a souterrain survives in the interior, an underground stone-lined passage or chamber that was a common feature of raths, used variously for storage, refuge, or as a place to keep dairy produce cool. A second rath lies approximately two hundred and fifty metres to the east-south-east, across the river, suggesting this stretch of the Deenagh valley once supported a small but meaningful cluster of early medieval settlement.