It follows the ghost of something much older, tracing the arc of an early medieval ringfort that has otherwise been absorbed back into the ground.

A rath, as this type of monument is known, is a roughly circular enclosure defined by an earthen bank and, typically, an outer ditch, used during the early medieval period as a defended farmstead. The Derrygeel example was recorded in 1977 as a raised circular area roughly 19.2 metres in diameter, enclosed by a bank of earth and stone with an external fosse, the term for a defensive ditch dug around such an enclosure. A break in the bank on the north-east side, accompanied by a causeway crossing the fosse, was interpreted as the likely site of the original entrance, a common feature in raths of this type. By the time the record was compiled, the monument had already been levelled, leaving only the curving field boundary from south-east through south to north-west, and a low rise in the ground elsewhere, as visible evidence of its former circuit.

What makes the site quietly interesting is precisely how little is left, and yet how legible it remains once you know what to look for. The surviving field boundary did not follow its unusual curved path by accident; at some point a farmer or surveyor simply incorporated the old earthwork into the landscape's working geometry, and it has remained there ever since, an unintentional outline of an enclosure that predates any map of the area by many centuries.