But the slight rise of ground around its perimeter is not incidental topography. It is the surviving scarp of a ringfort, a type of enclosed settlement built across Ireland during the early medieval period, typically between roughly 500 and 1000 AD, when farming families constructed earthen banks and ditches around their homesteads for protection and to define their territory.

The enclosure at Coolaboy is oval in plan, measuring 26.6 metres north to south and 21.5 metres east to west. Its defining feature is a scarped edge, essentially a steeply cut earthen bank, which reaches 2.1 metres in height and 1.8 metres in width at its best-preserved stretch, running from the south-east around to the south-west. Moving north-eastward, the scarp diminishes considerably, dropping to around 0.55 metres in height and spreading to roughly 4 metres in width, suggesting that this section has weathered or been disturbed over the centuries. Hedging runs along the top of the bank throughout, which is common in the Irish countryside where old earthworks have long been incorporated into field boundaries. The interior, now under rough pasture, has a dip about 1.8 metres wide running roughly east to west across its centre, the origin of which the site notes do not explain. The record was compiled by Denis Power and uploaded in August 2011.

The site is not signposted and there is no formal public access, but its location on the northern outskirts of Dromcolliher means it sits close to the ordinary fabric of the town rather than deep in agricultural land. The enclosure is entered through two small wooden gates set into the hedge, one at the north-north-west and one at the south-west. An ESB electricity pole standing atop the scarp at the north-north-east is a jarring modern intrusion but also, in a way, a useful locating detail. The best-preserved section of the earthwork is the south to south-west arc, where the full height of the scarp gives the clearest sense of what the original enclosure must have looked like before centuries of farming, grazing, and gradual erosion worked their way around the rest of the bank.