This is a rath, sometimes called a ringfort, the most common monument type in Ireland, yet familiarity has done little to dim the strangeness of encountering one in person. Ringforts were typically enclosed farmsteads of the early medieval period, their banks and ditches serving as much for the management of livestock and the marking of social status as for any serious military defence. What makes Rathnapoura worth pausing over is precisely how much of its original structure has endured.

The earthwork measures roughly 28 metres in diameter and is defined by two concentric banks with a fosse, or ditch, running between them. At the south-west of the inner bank, stone-facing is still visible, a detail that suggests the original builders reinforced their earthwork with masonry, a more substantial investment than the simple dumped-earth construction found at many comparable sites. The outer bank and fosse survive along the western and north-western arc, though the inner bank has been broken by several gaps over the centuries. The site was noted by Athy in 1914 and again by McCaffrey in 1952, meaning its presence in the scholarly record stretches back over a century, even if it has attracted little popular attention in that time.