Sitting across the northern end of a low, narrow ridge of pasture in County Kildare, this earthwork is remarkable less for what survives than for the sheer scale of what was once here. The enclosure measures roughly 108 metres in external diameter, making it a genuinely large example of its type. Earthen enclosures of this kind are among the most common yet least understood monuments in the Irish landscape; they may have served as ringforts for settlement and livestock protection, as ceremonial spaces, or as boundaries of a more territorial nature. Whatever its original purpose, the Grangebeg example has endured centuries of agricultural attrition with at least some of its form still legible on the ground.

The monument consists of two concentric earthen banks separated by a flat-bottomed fosse, a term for a ditch cut into the ground to provide both a physical barrier and material for the banks thrown up on either side. The inner bank, which retains a respectable external height of around 1.7 metres on its better-preserved northern and eastern sides, has been dug away almost entirely along the south, and largely levelled between the south-west and north-west. The outer bank, meanwhile, survives only along the northern arc. Immediately to the west, abutting the monument between the south-west and north-west, is a sunken trapezoidal area roughly 65 metres long and bounded by scarps up to 1.8 metres high on its north and south sides, closing at its western end against a natural hillock. This feature is considered likely to be a later addition rather than an original part of the design, though its function is not recorded.

The monument sits in pasture, and the ridge setting, though modest in height, would have given the enclosure a degree of local prominence. The northern and eastern stretches of the earthworks, where both bank and fosse are best preserved, offer the clearest sense of the original profile, and it is there that the relationship between the two concentric elements is most readable.