At this ringfort in Derra, north County Kerry, the watercourse curves around the northern and northeastern edge of the enclosure, filling in naturally where an artificial ditch would otherwise have been dug. It is a small but telling detail, suggesting that whoever chose this spot in early medieval Ireland was paying close attention to the landscape before they broke ground.

The site is a univallate rath, meaning it has a single enclosing bank rather than the multiple concentric rings found at more elaborate examples. A rath, in broad terms, is a circular earthwork enclosure, typically dating from the early medieval period and associated with a farmstead or settlement of some local standing. This one encloses a roughly circular space measuring 33 metres north to south and 33.4 metres east to west, making it a fairly typical example in terms of scale. The earthen bank surrounding it varies considerably in external height, between 1.2 and 2.4 metres, and sits on average about 0.8 metres above the interior ground level. Beyond the bank, a fosse, that is a ditch, runs around most of the circuit. It is U-shaped in profile, approximately 2 metres wide and 0.6 metres below the level of the surrounding land. Where the stream passes along the northeastern to eastern edge, the fosse is absent, the water having made it redundant. The site is documented in C. Toal's North Kerry Archaeological Survey, published in 1995, which catalogued a wide range of monuments across the region.