The rath at Coolagowan is a ringfort, a type of enclosed circular settlement built predominantly during the early medieval period in Ireland, roughly between the fifth and twelfth centuries, and used as a farmstead and place of security for a family and their livestock. What survives here is a bivallate example, meaning it has two concentric earthen banks rather than one, a feature generally associated with higher-status occupants.

The site was recorded and compiled by Denis Power, with notes uploaded in August 2011. The enclosure is roughly circular, measuring 36.4 metres north to south and 36 metres east to west. Two earthen banks survive in varying condition, separated by a flat-bottomed fosse, that is, a ditch, approximately 3.1 metres wide and now partly choked with rushes. The inner bank, though only about 0.3 metres high on its interior face, rises to 1.1 metres externally and is heavily covered in trees and scrub. The outer bank is considerably more worn, standing no higher than 0.5 metres on its inner side, and has been cut through on the eastern and southern flanks by later field boundaries, leaving it clearly visible only along the south-western to north-eastern arc. A causeway entrance roughly 2 metres wide survives at the north-west, while a separate gap of about 2.5 metres breaks the inner bank alone at the north-east.

The site sits in undulating, marshy ground, so firm footwear is advisable and the going can be soft underfoot at any time of year. The interior is level and under pasture, offering little drama once inside, but the tree-covered inner bank gives the enclosure a quietly enclosed character from certain angles. The outer bank is easiest to trace along the north-western arc, where it remains most intact; elsewhere, following the line of the old field boundary helps locate where it once ran. The rush-filled fosse between the two banks is the most readable feature on the ground, giving a clear sense of the original concentric structure even where the banks themselves have been reduced.