The site at Tonrevagh is a rath, the most common type of ringfort found across Ireland, typically a raised enclosure bounded by an earthen bank and ditch that served as a farmstead during the early medieval period, roughly 500 to 1000 AD. What makes this one quietly interesting is not grandeur but persistence: the scarp that defines its subcircular outline, running approximately 21.5 metres north to south and 18.5 metres east to west, remains in fair condition, holding its shape in the landscape long after whatever wooden structures once stood inside have vanished entirely.

More intriguing is a small grassed-over stone structure within the interior, measuring just 1.5 metres in length and 1.2 metres in width, oriented north to south. Its function is not recorded. It could represent the remains of a small outbuilding, a souterrain entrance, which is an underground stone-lined passage used for storage or refuge, or simply a later field feature unrelated to the original enclosure. Without excavation, it keeps its own counsel. The site was documented as part of the Archaeological Inventory of County Galway, Volume II, covering North Galway, compiled by Olive Alcock, Kathy de hÓra, and Paul Gosling and published in 1999, a systematic effort to record the kind of monument that can disappear quietly beneath a plough or a drainage scheme before anyone thinks to look closely.