The ringfort, a type of circular enclosure typically used as a defended farmstead during the early medieval period, measured roughly forty metres across and sat on the west-facing slope of a low hill, the kind of quiet, practical position that early farmers favoured for shelter and drainage.

The oldest Ordnance Survey six-inch map recorded it clearly as a complete circular enclosure. By the time the third edition was produced in 1932, only the north-western sector remained visible, suggesting gradual erosion or agricultural pressure across the intervening decades. The end came definitively in the mid-1960s, when, according to local information, the monument was levelled during land reclamation works. A second enclosure nearby, recorded separately, was lost at the same time. The 1960s saw considerable agricultural intensification across Ireland, and ringforts were frequently cleared to improve field drainage or increase tillage and pasture land, sometimes with grant assistance. Thousands were lost across the country during this period, and the Crumlin example was among them.