Locally known as the "hill of the skull", the esker at Cleghile is a natural glacial landform, a long gravel ridge deposited by meltwater, running roughly east to west across the landscape. At its western end, the ground has been deliberately shaped: the ridge was scarped, meaning its sides were cut back and steepened, to create an irregular earthwork measuring roughly 130 metres along its length and 32 metres across, with a scarp standing less than a metre high. The place has been further altered by the arrival of a railway line immediately to the south, whose embankment now incorporates part of the earthwork, and by a road that cuts through its southern portion. When that road was being excavated, and again during work on the railway embankment, human bones were uncovered beneath the soil.

The name "hill of the skull" may not be coincidental. Writing in 1913, a local commentator named Flynn proposed that the townland of Cleghile, along with the neighbouring townlands of Corrogemore and Corrogebeg, corresponds to an early medieval area recorded as Cnamchoill. The name in Irish carries connotations of bone and wood, and the annals associate Cnamchoill with a battle fought between Brian Boru and the Danes. Flynn identified Cleghile itself as the probable site of that engagement, and noted that bones continued to be turned up occasionally in the townland, described in local memory as the skeletons of "very tall men". Whether the earthwork was a pre-existing feature that made the ground strategically useful, or whether it relates directly to activity surrounding the battle, remains an open question. What is clear is that the ridge, reshaped by human hands at some point in the past, has been giving up its dead in fragments ever since, absorbed quietly into the fabric of a railway line that most passengers cross without a second thought.