The enclosure measures thirty-six metres in diameter, its perimeter marked not by a dramatic earthen bank but by a rise in the ground that reaches no more than sixty centimetres at its highest point. The interior dips gently inward in a saucer shape, giving the whole structure an almost accidental quality, as though the land simply settled here long ago and never quite levelled out.

Ringforts, known in Irish as raths when constructed from earthen banks and ditches, are among the most numerous archaeological monument types in Ireland, with tens of thousands recorded across the country. They served primarily as enclosed farmsteads during the early medieval period, roughly between the fifth and twelfth centuries, protecting a family's home and livestock from opportunistic raiding rather than from organised military assault. The example at Tullyglass follows the characteristic circular plan, and its south-facing slope would have offered both shelter and good light, a practical consideration that early farmers shared with those who build houses today. The modest scale of the surviving earthwork suggests centuries of agricultural activity have worn the banks down considerably from whatever height they once held.