The raised platform, roughly fifty metres across, sits on a gentle swell in what is otherwise an undulating, low-lying landscape, its edges softened by grass and scrub and a perimeter hedge. A flat-bottomed fosse, the kind of encircling ditch that once helped define both the physical and social boundary of an early medieval farmstead, runs around much of its circumference, varying in depth from about half a metre on the southern side to nearly one and a half metres on the north. A roadway skirts the northeast to southeast arc, a reminder that later generations simply worked around what earlier ones had left behind.

Ringforts, known in Irish as raths when they are earthen rather than stone-built, were the most common form of enclosed settlement in early medieval Ireland, typically home to a single farming family of some local standing. Most date from roughly the sixth to the twelfth centuries, though many remained in use or in memory long after that. The Costrea example fits the general type well enough: a raised interior platform, an enclosing bank, a fosse, and formerly some kind of entrance gap. That entrance, however, has not been identified with any certainty, which means the original orientation of the site, and what it faced towards or away from, remains an open question. The site was recorded and measured as part of Michael J. Moore's Archaeological Inventory of County Leitrim, published by the Stationery Office in Dublin in 2003.