The site at Kilnaslieve sits on the south-facing slopes of Cat Hill, in ordinary grassland, and what remains is barely legible as a human construction at all.

The monument is a rath, the Irish term for a ringfort, a type of enclosed farmstead typically dating from the early medieval period, roughly 500 to 1000 AD, though examples were built and used across a wider span of centuries. Thousands of them survive across Ireland in varying states of repair; this one is not among the better-preserved. It is subcircular in plan, with a diameter of around 29 metres, and what now defines it is a scarp, a low earthen slope or edge, rather than any upstanding bank or wall. That scarp runs from the north-east, around through the south, and back up to the north-west, tracing most of the circuit. The northern arc, where the road passes through, is lost entirely. At 29 metres across, it would have been a modest enclosure, likely the homestead of a single farming family rather than a seat of any particular power.