Five-stone circles are a distinctive and largely Cork-Kerry phenomenon, characterised by a pair of portal stones, two flanking stones, and a single lower axial stone placed opposite the entrance, the whole structure oriented along a deliberate astronomical axis. At Knocknakilla, that axis runs roughly north-north-east to south-south-west. The circle is modest in scale, the orthostats standing between 1.3 and 1.5 metres tall, but what makes the site quietly unusual is its immediate neighbourhood: a pair of standing stones sits roughly three metres to the south-west, and a radial-stone cairn, a Bronze Age burial monument built with stones arranged like spokes radiating outward, lies just seven metres to the east. Three distinct monument types, set within a few strides of one another.

When the Cork-born museum curator L. S. Gogan visited on the 8th of July 1931, he found the circle complete and its interior flagged, with a considerable quantity of quartzite stones scattered around the entrance. No finds were recovered from the investigation. Since Gogan's time, at least two of the uprights have shifted: the axial stone and the stone on the eastern side had both fallen by the time later researchers documented the site. Seán Ó Nualláin, who systematically catalogued the stone circles of south-west Ireland, recorded Knocknakilla in his 1984 survey, placing it within the broader pattern of Cork-Kerry five-stone circles, many of which share this same axial alignment and compact internal geometry. The monument holds a preservation order dating from 1941, one of the earlier such protections issued under Irish national monuments legislation.