The circular enclosure at Corlattallan measures roughly 37 metres across and belongs to the class of monument loosely called a ring-fort, an earthen or stone-defined enclosure typically associated with early medieval settlement and farming life in Ireland, though the term covers a wide range of forms and dates. What gives this particular example an odd, layered quality is that its outer bank has been absorbed into the townland boundary of Corlattallan itself, and probably also incorporates a field bank with a later re-cut drain running alongside it. The ancient and the agricultural have merged here to the point where separating one from the other is largely guesswork.

The enclosure is defined by a slight inner earthen bank, standing about 0.65 metres above the interior and 1.65 metres above the exterior on its south-western side, and separated from a larger outer bank by a fosse, which is the term for the ditch or trench typically dug to provide material for the banks on either side of it. At the south-west the fosse measures over six metres wide at the top and about two and a half metres at the base. These are modest but legible dimensions. The complication is that the defining features survive only around the southern, western, and northern arc; the north-east to south section of the perimeter cannot be traced, partly because a modern house and garden sit just outside the enclosure to the east. It is a common enough situation with monuments of this kind, where the edges of early settlement gradually disappear beneath later buildings and cultivation, leaving only the portions that happened to escape improvement or development.