The site is a rath, the Irish term for a ringfort, which were circular enclosures typically built during the early medieval period as farmsteads for single families or small communities. They were defined by one or more raised banks and ditches, and several thousand survive across Ireland in varying states of repair. The example at Corgerry Eighter is more elaborate than most, in that it once had three concentric banks with two intervening fosses, or ditches, between them. A multivallate ringfort of this kind, with multiple defensive rings, is generally thought to have belonged to someone of higher social standing than the occupant of a simpler, single-banked enclosure.

The site measures approximately 38 metres in diameter and sits in level grassland, which means it lacks even the advantage of elevated ground to make its earthworks legible at a glance. Of the original three banks, only the innermost survives with any continuity, running from the south, around through the west, and up to the north. A trackway runs just outside this inner bank. The outer banks and their accompanying fosses are readable only from the north to the north-east, where they have escaped whatever combination of agriculture, erosion, and time has reduced the rest to almost nothing.