The earthen bank that circles the interior remains largely intact, and the gap cut into the eastern side, just 0.6 metres wide, is exactly the kind of narrow opening designed to let livestock through while keeping larger threats out. That the site continues to function as pasture is, in its way, a form of unbroken continuity.

A rath, as this type of ringfort is known when built from earth rather than stone, typically consists of a raised interior enclosed by one or more earthen banks with an accompanying ditch, or fosse, on the outer side. They are among the most common archaeological monument types in Ireland, associated broadly with the early medieval period, and were used as farmsteads or enclosed settlements for people of relatively modest status. The Derrishal example is modest in scale but well-preserved in its proportions: the circular enclosure measures roughly 34 metres north to south and 33 metres east to west, with the bank standing nearly a metre high on the interior face and slightly higher, at around 1.18 metres, when measured from the base of the external fosse. The main entrance, a causewayed gap facing south, is four metres wide, wide enough for a cart or animals moving in number. The interior sits slightly raised above the surrounding ground, a characteristic that often results from centuries of accumulated occupation material, though here it may equally reflect the original ground-shaping during construction.