A fosse is the ditch cut between the earthen banks of a ringfort, typically intended as a defensive barrier, and finding active water sources within one is unusual enough to give pause. Most of Ireland's several thousand surviving ringforts are straightforward in their layout; here, the fortification and the water supply have ended up sharing the same space.

The site itself is a circular rath, a type of enclosed farmstead common in early medieval Ireland, roughly 70 metres in external diameter and still in fair condition despite the centuries. It sits in undulating grassland in Lissaniska, County Galway, defined by two concentric banks with the fosse running between them. A causeway entrance survives on the southern side, which is the conventional approach for raths of this kind. The interior, however, is now densely overgrown, which makes reading the ground surface difficult and suggests the site has been left largely undisturbed for some time.