And yet someone did exactly that, crowning the flat summit with a ring-wall of large, close-set boulders so precisely fitted to the available space that the enclosed area, roughly fifteen to sixteen metres in diameter, takes up almost every usable metre at the top. The knoll is an anomaly in its own right: it sits at the southern edge of a rocky plateau, with the sea visible to the west and a broad sweep of lowland pasture rolling away to the south, the kind of vantage point that would have made its occupants visible, and watchful, from a considerable distance.

Thomas Johnson Westropp, writing in 1905, called it the 'curious, though much levelled, hill-fort of Croaghateeaun' and recorded the foundations of a strong ring-wall with walls between 2.43 and 3.35 metres wide, built from substantial blocks measuring up to 1.82 metres in length. He described and drew a SSE-facing entrance faced with large stones and notably widening inward, a design feature sometimes associated with defended gateways. By the time of his visit the structure was already poorly preserved, though foundations remained visible. Writing later, in 1980, George Cunningham used the Irish name Cruach An tSidheain, which translates roughly as the fairy mound or fairy hill, and described it as 'crowned by a small but strong fort', a turn of phrase that quietly acknowledges both the folklore attached to the place and the solidity of what was built there. The Irish name hints at the kind of otherworldly reputation that often accumulated around prehistoric enclosures, particularly those on elevated, isolated ground.

What survives today is a rough circuit of contiguous large boulders following the summit edge, with the natural rock outcropping itself forming part of the perimeter on the south-western to north-western arc, its vertical external face doing the work of dressed stonework. A possible entrance gap at the north-north-west faces the more gently graded northern slope of the knoll, and on that same slope a narrow raised spine of ground curves downward in a natural ramp-like line. Whether this was ever deliberately shaped or reinforced as a pathway to the summit is uncertain; some of the stones along its outer edge may be the remnants of walling, or may simply be what the hill was always made of. Dense hazel scrub now encircles the base and has crept up the northern and eastern slopes, softening a landform that, seen from a distance, reads as something older and more deliberate than the surrounding plateau.