It measures roughly 35 metres across, raised slightly above the surrounding ground on a low platform, with a scarp of only about 20 centimetres at its edge. That modest rise is nearly all that announces it. The trees that once defined it are gone, and a pit dug into the eastern half suggests the ground has been quarried at some point. What you are looking at, most likely, is a tree-ring.

Tree-rings were a feature of designed demesne landscapes, typically from the eighteenth or nineteenth century, in which trees were planted in a deliberate circle, often for ornamental effect and sometimes as a shelter belt or a visual focal point within a gentleman's estate. They were a way of imposing geometric order on open ground, and on early Ordnance Survey six-inch maps this one was faithfully recorded as a circular tree-planted enclosure. A faint darker band of vegetation on the northern side hints at a possible external fosse, a shallow ditch that would have helped define the boundary of the planting, though the evidence is slight. The Castle Ffrench demesne itself belonged to the Ffrench family, one of the old Catholic gentry families of Connacht who retained their lands and social standing across a particularly turbulent period in Irish history. The designed landscape around their house would have been a mark of that status, laid out with the kind of careful informality that Georgian estate fashion demanded.