The site at Cahererillan is a cashel, a type of ringfort defined by a drystone rather than earthen boundary wall, and its roughly circular plan, measuring approximately 34 metres east to west and 30 metres north to south, is still legible in the landscape. What makes it quietly unusual is the layering: at some point after the cashel was built, a tower house was constructed within its south-western quadrant, and the old enclosure wall appears to have been repurposed as a bawn, the defended enclosure that typically surrounds an Irish tower house to protect livestock and offer a first line of defence. The original became useful again, simply reframed.

The cashel wall survives in fair condition, with a possible entrance gap on the south-eastern side. Running southward from the western edge of that gap is a trace of linear walling, about 13 metres long, which may have been associated with the original enclosure. A later field wall cuts through the interior from roughly north to south, adding another layer of agricultural reorganisation to a site that has been pressed into service across multiple periods. In the north-eastern quadrant, traces of two further buildings are still visible, and several house sites can be made out to the south-west, suggesting that what survives above ground is only a portion of a once busier complex of structures clustered around or within the enclosure.