A cashel is a ringfort enclosed by a stone wall rather than an earthen bank, and this one at Lios Na Caolbhuí is unusual not simply for its circular enclosure but for how much of its own complicated history is still legible in the stonework. A later field wall was built directly on top of the cashel's original perimeter, and the two can be distinguished by eye: the lower 0.85 metres of the original construction uses considerably larger stones, while the rebuild above sits noticeably further back from the inner face. The probable original entrance, a 4.5-metre gap on the eastern side, is now blocked where that field wall crosses it.

Inside the 21.2-metre enclosure, the remains of three separate hut structures can be traced. The largest, in the northwest, is a circular stone hut nearly six metres in internal diameter, with its entrance gap still visible on the south-south-east side. Immediately east of centre, a second and much more ruined hut survives only as a horseshoe-shaped depression in the ground, open to the south-east, and possibly once joined to its neighbour. A third, oval or sub-rectangular in plan, abuts the enclosing bank at the south-south-west. There is also a souterrain, an underground stone-lined passage of the kind used in early medieval Ireland for storage or refuge, running somewhere beneath the interior. It is no longer accessible, but a section of its drystone passage is exposed where one or two roofing slabs have collapsed or been removed, leaving a depression on the northern side. The passage appears to run roughly towards a small lintelled opening through the cashel wall at the north-north-east, though whether the two were connected is not known. To the south, the enclosing bank merges with a stony mound that may simply be the accumulated debris of a field wall cleared from the western perimeter at some point, its original purpose already forgotten by whoever did the clearing.