The rath at Rathduff in County Mayo has three. That alone would set it apart, but what makes it stranger still is the contrast between its formidable earthworks and its current condition: the interior is entirely choked by thorn bushes and brambles, and the banks themselves are densely ringed by hazel scrub, making the whole structure feel less like an archaeological monument and more like something the landscape has quietly reclaimed.

The earthwork sits on a low ridge in pasture, with open views westward towards Lough Conn, roughly 700 metres away. The raised circular area measures between 30 and 35 metres in diameter, and its three concentric earthen banks, separated by two fosses (the ditches that accompany a bank as its material was dug outward), are substantial. The innermost bank alone rises to around 2.3 metres on its exterior face at the south-east; the outermost bank reaches nearly 6 metres in width. Stones visible on the inner face of the inner bank may be the remains of original stone facing, and further stones protrude from the outer banks, though whether these are structural remnants or simply chance inclusions is not clear. The original entrance was almost certainly on the east side, where a gap of around 3.4 metres survives in the inner bank, with corresponding breaks in the two outer banks. Those outer gaps have been widened considerably in the modern era, presumably for agricultural access, and the outermost bank has been incorporated into a field boundary along its eastern and south-western arc. There are also narrower breaks through all three banks on the western side. A second rath lies just 90 metres to the north-west, which raises the intriguing possibility that the two enclosures were contemporary, or at least related.

The triple-bank arrangement is a rarity. Most scholars associate such elaborated ringforts with higher-status occupants, the additional earthworks serving as a signal of rank as much as a practical defensive measure. Whether that interpretation holds here is unknown, but the effort involved in throwing up three concentric banks with their intervening ditches, on a ridge with clear sightlines to one of Mayo's larger loughs, suggests that whoever built this place had both the resources and the reasons to make a considerable impression.