It occupies a south-facing slope, its circular enclosure measuring roughly 28 metres across internally, with an overall diameter stretching to about 42 metres once you account for its earthworks. A ringfort, sometimes called a rath, is an enclosed farmstead of the early medieval period, typically dating from around the fifth to the twelfth century, and this one preserves its basic anatomy well enough to read in the landscape.

What survives at Colvinstown is a combination of an earthen bank and a fosse, the latter being the external ditch from which material was originally dug to raise the bank. The bank runs from the west around to the north-east, reaching up to 1.2 metres in height and between two and two-and-a-half metres wide. The fosse alongside it is notably substantial, measuring 4.5 metres across and dropping to a depth of 1.7 metres at its deepest point. Where the bank and ditch give out, the interior is defined instead by a steep natural or artificially scarped edge. A possible entrance, roughly two metres wide, is visible on the northern side, with boulders flanking it on one side. No internal features have been identified within the enclosure, so whatever structures once stood there, a house, outbuildings, perhaps a souterrain or underground passage, have left nothing legible at the surface.