The one sitting on a hilltop in Ballybaun, Co. Clare, is a little different: its southern edge runs straight for some fourteen metres, giving the whole enclosure a roughly D-shaped outline that sets it apart from the classic form. It is an oddity that easy to miss unless you are looking closely, yet it has been visible on maps since at least 1840, when the Ordnance Survey recorded it as a circular hachured enclosure on their six-inch sheets. The same feature appeared again on the 1916 edition, patient and unchanged, while the rough pastureland around it carried on its seasonal business.

A rath, to use the Irish term, is an earthwork enclosure, typically dating from the early medieval period, built as a farmstead and defined by one or more banks and ditches. This example measures roughly 26.8 metres east to west and 26.7 metres north to south, making it a modest but well-preserved specimen. The enclosure sits on a flat-topped platform that tilts gently eastward, and the height of the bank above the surrounding fosse, the external ditch, shifts as you move around it: 1.9 metres on the western side, dropping to 1.3 metres at the north and 0.9 metres to the east. Between the base of the platform and the inner edge of the fosse on the western side there is a narrow berm, a level shelf of ground roughly 0.8 to 1 metre wide, which would have helped stabilise the structure. The flat-bottomed fosse itself survives almost continuously around the site, interrupted only at the east-north-east by a modern ramped gap, the kind of practical intrusion that centuries of agricultural use tend to leave behind. Traces of an outer bank, low and flat-topped, are still readable from the south-west round to the west. A silted-up leat or drainage channel, once presumably managed to keep the fosse clear, branches off to the north-west, a small detail that hints at the careful maintenance these enclosures once required.