It was a bivallate enclosure, meaning it was defined by two concentric earthen banks and their accompanying ditches, a form of enclosed settlement typical of early medieval Ireland. Sites of this type were once scattered across the Irish landscape in their tens of thousands, most likely serving as the farmsteads of prosperous farming families between roughly the sixth and tenth centuries.

The Granshagh ringfort was recorded on the Ordnance Survey map of 1841 to 1842, when the great national mapping project was capturing Ireland's topography in remarkable detail. It appeared again on the 1916 edition of the same mapping, though by that point the outer bank had already vanished from the cartographic record, suggesting the earthworks were already being diminished. As late as 1974, aerial photographs taken by the Geological Survey of Ireland showed the site still legible from the air, the buried or low-lying traces of the banks casting faint shadows or tonal differences across the ground. At some point after that, the site was levelled entirely. What the 1974 photographs captured was, in effect, one of its final appearances as something recognisable.

There is nothing to see at ground level today. The value of the Granshagh ringfort now lies less in any physical remains than in what its documented decline illustrates about the attrition of archaeological sites across agricultural Ireland, a process that happened field by field, generation by generation, often entirely within the law and without any particular notice.