The enclosure itself is substantial enough, a sub-circular ring roughly 44 metres north to south and 46 metres east to west, defined by an earthen bank and a wide, deep external fosse, the term for the ditch that typically surrounds a defended enclosure of this kind. A causeway, still measurable at 3.2 metres wide and 0.35 metres high, carries the original entrance across the fosse on the eastern side. But it is the interior mound, just 5.8 metres in diameter and 0.4 metres high, that draws the eye and resists easy categorisation. It may be a barrow, a low burial mound of the kind found across Ireland from the Bronze Age onward, or it may be something else entirely.

The 1657 Down Survey, a remarkable Cromwellian-era mapping project that documented land ownership across Ireland with unusual precision, places a structure called 'Rinechan Castle' in this general area of Fore barony and St. Feighin's parish. The suggestion put forward by researchers Frank Coyne and Caimin O'Brien is that the enigmatic central mound may be all that now remains of the levelled castle of Ranaghan, its stonework long since robbed out and the ground slowly settling into a low earthen rise. The interior also preserves faint traces of cultivation ridges running west-northwest to east-southeast, a reminder that this landscape has been worked and re-worked over many centuries. A separate ringfort lies approximately 300 metres to the northwest, adding to the sense that this corner of Westmeath was once a good deal more populated and organised than its current pastoral quiet suggests.