Even then, the classification was hedged: "Enclosure, possible." That qualifier carries a certain weight. Thousands of ringforts, or raths, survive across Ireland, the enclosed farmsteads of early medieval farmers and landholders, typically defined by a circular bank and an outer ditch known as a fosse. At Tullassa, the ditch has gone entirely, and the bank itself has been reduced to a grass-covered arc that barely rises above the surrounding ground.

What survives is an earthen bank running roughly south-west to north-east across a span of around eighteen metres, and about seventeen metres across the perpendicular. The bank measures between three and 3.8 metres wide, but its height is modest to the point of near-invisibility, standing between 0.2 and 0.6 metres on the interior and slightly less on the exterior face. Beyond that surviving arc, the rest of the enclosure's perimeter can only be detected as a faint scarp, dropping no more than a tenth of a metre. There is no visible entrance. A fragment of the bank was significant enough to be marked on the Ordnance Survey six-inch map in its 1921 edition, rendered in the small hachure lines cartographers used to indicate earthen slopes, which suggests the feature was still legible on the ground a century ago, even if only just.