The site at Cloonacalleen is a rath, the most common type of ringfort in Ireland, typically constructed as a raised circular or oval enclosure defined by earthen banks and ditches to enclose a family's dwelling and outbuildings. This one measures roughly 50 metres east to west and 42 metres north to south, its boundaries now reduced to a scarp and an intervening fosse, the shallow ditch that once helped define the perimeter. Traces of an outer bank remain visible along the western to northern arc, suggesting the enclosure was once more substantial than what survives today.

What makes the site quietly compelling is a feature tucked within the interior: a probable souterrain. A souterrain is an artificial underground passage or chamber, typically stone-lined, associated with early medieval settlement in Ireland and thought to have served for storage, refuge, or both. Their presence within ringforts is relatively common across the country, though the particular function of any individual example is rarely certain. The Cloonacalleen souterrain remains unexcavated and unconfirmed, its precise character unknown, but its likely presence beneath this already subdued earthwork adds a layer of concealment to a site that seems, on the surface, to have given very little away.