The arrangement is not as incongruous as it might seem; farmsteads have gathered around these ancient enclosures for centuries, sometimes obscuring them, sometimes preserving them, always complicating the picture for anyone trying to read the landscape clearly.

A rath, as this type of monument is known, is a roughly circular enclosure defined by one or more earthen banks and ditches, typically dating to the early medieval period in Ireland, between roughly the fifth and twelfth centuries. They served as defended farmsteads for individual family groups. At Lisgillan, the enclosure is subcircular in plan, measuring approximately 39 metres north-north-west to south-south-east and 35 metres east-north-east to west-south-west. The defining bank has been significantly reduced over time, surviving mainly as an external scarp; at the north-east it still reaches a height of around 4.2 metres. Between this inner bank and a second outer bank lies a flat-bottomed fosse, essentially a ditch dug to reinforce the defensive boundary. Both the outer bank and fosse survive only on the western and north-western arc of the monument. A widened gap at the south-east is thought to mark the position of the original entrance, a common placement that would have oriented the opening towards the more sheltered and accessible side of the ridge.