This one, sitting on a low rise in the rolling grassland of Castletown in County Galway, breaks that pattern: it is D-shaped, an asymmetry that gives it a quietly distinctive profile among the thousands of similar enclosures scattered across the Irish countryside.

The earthwork measures 36 metres east to west and 31 metres north to south, and it carries two banks with a fosse, or ditch, running between them, a layout that would have made it a reasonably substantial defensive enclosure in its time. A rath, to borrow the Irish term commonly used for this type of earthen ringfort, typically served as a farmstead for a family of some local standing during the early medieval period, roughly between the fifth and twelfth centuries. Here, the inner bank is traceable from the north-north-east around through the south and on to the west, while along other sections a natural or worked scarp takes over as the enclosing element. The outer bank and fosse are best preserved along the southern and western arc, swinging up towards the north, giving the site its lopsided but legible geometry.