The rath at Rathoonagh, a broadly oval enclosure measuring roughly 47 metres north to south and about 40 metres east to west, is the kind of site that asks something of its observer. Partly levelled at some point in the past, its defining banks and fosse, the wide flat-bottomed ditch that would once have separated the two earthen ramparts, are now so worn that in places they are readable only through the way different plants choose to grow. A field ditch has since been cut straight across the eastern edge, slicing through the fosse as if the old boundary simply did not register.

A rath is the Irish term for a ringfort, a circular or oval enclosure defined by one or more earthen banks, most commonly associated with farming settlements of the early medieval period, roughly the fifth to twelfth centuries. Thousands once existed across Ireland, and many were deliberately levelled as agriculture intensified. The Rathoonagh example survives in diminished form, though its builders made deliberate use of the landscape. A natural drop in the ground to the north was incorporated into the enclosing works, effectively borrowing topography to do some of the structural work. It sits in low-lying pasture, with a line of low hills visible to east and west, and a distant prospect of the sea to the north-north-west.

Today the interior is largely covered in rushes, and dense gorse and scrub obscure the north-east and eastern perimeter. The site reads more clearly from its edges than from within, and the differential vegetation, where reeds and scrub betray the line of the old banks, rewards a slow and patient look across the field rather than any direct approach through the undergrowth.