The cashel at Cahernagry, sitting on a low rise amid scrubland in County Galway, is the kind of site that rewards patience and a certain tolerance for ambiguity. A cashel is a stone-walled ringfort, the drystone equivalent of the more familiar earthen rath, and this one survives in a poor enough state that its shape is easier to read on paper than on the ground.

The enclosure is oval, running roughly 53 metres north to south and 23.5 metres east to west. What remains of the perimeter is a low drystone wall, though traces of inner and outer wall-facing are still visible along the western and northern stretches, suggesting the original construction was more substantial than what now remains. The townland boundary, a later administrative line in the landscape, overlies the enclosing wall from the north-east around through the east and south-east, which goes some way to explaining the degree of disturbance in that arc of the monument. At the south-east, an irregularly shaped annexe adjoins the main enclosure. Such annexes, sometimes used for livestock, sometimes as additional domestic or agricultural space, are not unusual features of ringfort complexes, though this one's outline is notably uneven.