The earthwork recorded here was once a rath, the Irish word for a ringfort, which was a type of enclosed farmstead typically used between the early medieval period and around the twelfth century. A rath usually consisted of a circular bank of earth, sometimes reinforced with timber or stone, surrounding a central living area and accompanied by a fosse, the drainage ditch from which the bank material was dug. At Coolnanoglagh, the bank itself is gone, and what remains is largely just the impression left behind.

According to local information compiled by Denis Power, the monument was levelled around 1980, when the bank material was used to fill in the fosse rather than simply removed. The site sits in level pasture and measures roughly 22 metres on its north-northeast to south-southwest axis and 18 metres east-west, making it a modest example of the type. The fosse, where it can still be read in the ground, is about 6.25 metres wide and survives to a depth of around 0.3 metres. It is not intact on all sides; the north-northwest to northeast section has been infilled, and a field boundary cuts across the southwest to north-northeast portion. What is left, then, is a partial outline at best.

The site sits in ordinary agricultural land and there is nothing to announce it to a passing visitor. Because the bank was deliberately demolished relatively recently, there is no upstanding earthwork to observe, and reading the landscape here requires some patience and ideally a knowledge of what to look for in low-light conditions, when slight variations in ground level become more legible. Early morning or late afternoon in autumn or winter, when the sun is low and shadows fall across shallow ground features, offers the best chance of seeing anything at all. The remaining fosse segments appear as gentle depressions in the grass rather than any dramatic feature. The interest here is less visual than conceptual: a site systematically erased within living memory, recorded formally only decades after the damage was done.