This is a rath, a type of ringfort that would originally have served as an enclosed farmstead during the early medieval period, typically defined by a raised bank, a fosse (a cut ditch running between banks), and a second outer bank forming a layered defensive perimeter. The one at Allykeolaun measures roughly 37 metres in diameter, which puts it within the typical size range for such structures, though very little of it now reads clearly in the landscape.

What survives is fragmentary. The fosse and the outer bank can still be traced along a roughly northeast to south-southwest arc, suggesting that the eastern and southern portions of the monument have held up better than the rest. At the eastern side, there is a possible entrance gap about four and a half metres wide, which would be consistent with the eastward orientation many ringforts favour. Two later field walls have been built across the monument at the northwest and northeast, and a third runs along the outside of the inner bank to the west. These walls, almost certainly of post-medieval agricultural origin, cut through and obscure what remains of the earlier structure, making it genuinely difficult to read the rath as a coherent whole.