It is a rath, or ringfort, the kind of early medieval farmstead enclosure that once dotted the Irish countryside in the thousands, built to define a family's territory and offer some protection for their livestock. What makes the one at Cloonlarhan quietly worth attention is how much of its original form has endured, even as the surrounding landscape has shifted around it.

The enclosure measures roughly 25.6 metres from northwest to southeast and 31.6 metres from northeast to southwest, giving it a broadly oval shape. A low earthen bank traces its perimeter, standing just over a metre high on the outer northern face and dropping to about half a metre on the south. The bank is modest, but in several places it is reinforced or faced with stone, particularly where later field fences have been built up against it at the northeast, east, and southwest. Those fences tell their own story: farmers in subsequent centuries found it practical to use the old structure as a ready-made boundary, embedding the ringfort into a working agricultural landscape rather than clearing it away. There are several narrow breaks in the bank, likely the result of erosion over time, and a noticeably stony section at the southwest that may once have been a proper entrance, later filled in. The interior is flat, grassy, and level with the surrounding ground, fringed with hawthorn and brambles. To the north, the land falls away towards a broad expanse of bog, much of it now given over to forestry plantation, which would once have formed a natural, marshy boundary on that side.