Drumlins are the smooth, elongated hills left behind by retreating glaciers, and they define much of the landscape across this part of Ireland, their rounded backs rising and falling in tight succession. Near the top of one such slope at Drumsillagh, on the north-east-facing side, sits a modest planted enclosure roughly fifteen metres across in either direction, triangular in form, tucked to the south-west of a farm lane running northwest to southeast.

What makes it quietly odd is the shape-shifting documented by the Ordnance Survey maps. The first detailed survey of this area, the OS six-inch map of 1835, shows a triangular enclosure on this spot. By the 1907 edition, the same feature is rendered as D-shaped. Whether this reflects an actual change to the boundary on the ground, a difference in how individual surveyors read and recorded the same planting, or some genuine reorganisation of the land in between, is not clear from anything that survives. The trees themselves remain, and the enclosure today reads as triangular again, small and self-contained in the field. Planted tree-rings and designed landscape features of this kind were sometimes used as shelter belts, as ornamental markers, or simply as practical windbreaks on exposed agricultural land, and the drumlin position here would have made the site reasonably prominent in the local view.