Set on its summit is a cashel, the Irish term for a stone-walled enclosure of early medieval origin, and this one at Ballinlough is notable for its double-ring design: two concentric banks enclosing a fosse, which is the formal term for a ditch, between them. The fosse here was cut directly into the bedrock, which gives some sense of the effort involved in its construction. A causeway crosses it on the south-west side, where breaks in both banks mark the original entrance. The overall diameter of the enclosure runs to approximately 150 feet, or around 46 metres, making it a fairly substantial structure.

The most detailed account of the site comes from a survey carried out by O'Kelly in 1942 to 1943 and published in the following year. That description noted the banks as being composed of small stones mixed with earth and gravel, and drew attention to a semi-circular wall within the south-east quadrant of the interior. Set between this wall and the outer rampart, it was interpreted at the time as a possible hut site, with its greatest dimension recorded at roughly 45 feet, or 14 metres. Cashels of this type are generally associated with the early medieval period in Ireland, often serving as farmsteads or the enclosed settlements of local families, and the use of a natural rock formation as a foundation would have offered both practical and defensive advantages.

The enclosure remains visible from aerial photographs, including images held by the Archaeological Survey of Ireland taken in August 2000 and October 2002, where its outline shows clearly from above. On the ground, the double-bank arrangement and the causeway across the fosse are the features most worth picking out. The site sits on a knoll, so the approach will involve a modest climb, and the limestone underfoot can be uneven. Visiting outside the growing season, when vegetation is lower, tends to make the structural details easier to read.