This is a rath, the Irish term for a ringfort, a type of enclosed farmstead typically built during the early medieval period, roughly between the fifth and twelfth centuries. Tens of thousands of them survive across Ireland in various states of preservation, but what makes this one worth a second look is precisely its ordinariness and its persistence: old enough to have shaped the landscape, yet practical enough to have been folded into the working of it.

The platform measures approximately 37.8 metres north to south and 42.6 metres east to west, making it a reasonably substantial example of the type. Its defining bank and scarp have been absorbed into agricultural use at different points around the circuit. On the north-east to south arc, an earth and stone bank survives with an internal height of around 0.9 metres and an external face of 1.7 metres. Further round, from south to west, the original scarp has been reduced to about a metre in width and crowned with a post and wire fence. On the western to northern stretch, the scarp has been cut back to a near-vertical face, reaching 2.2 metres at its highest point to the north-north-west. The interior is flat and grassy, with hawthorn and ash trees ringing the perimeter, and a modern house garden sits just a few metres to the north. A second rath lies 220 metres to the north-east, suggesting that this part of Tonroe was once home to more than one early medieval household, each occupying its own enclosed ground on the same stretch of terrain.