The enclosure is modest, measuring roughly 26.5 metres north to south and 20 metres east to west, but its proportions are typical of the rath, a class of monument that once numbered in the tens of thousands across Ireland. A rath is essentially a circular or oval enclosure defined by one or more earthen banks and ditches, used as a defended homestead during the early medieval period, broadly the fifth to twelfth centuries. Most were the homes of farming families of middling social rank, their banks serving less as serious fortifications than as markers of status and boundaries for livestock.

What survives at Cooga is a low earthen bank, about 3.2 metres wide, that still stands roughly a metre high on its exterior face, though the interior height has been reduced to around 35 centimetres. The southwestern section has been levelled entirely, whether by agricultural clearance or simple erosion is not recorded. More quietly interesting are the traces of stone facing visible on the bank, suggesting that at some point its earthen core was revetted or reinforced with stone, a detail that distinguishes it slightly from plainer earthwork examples and hints at a degree of care in its original construction.