The site known as Castlebin Fort is now so poorly preserved that it takes a degree of patience and a certain willingness to read landscape to make much sense of it. What survives is a roughly D-shaped enclosure, measuring approximately 45 metres east to south and 40 metres north-northwest to south-southeast, defined partly by a scarp, which is essentially a steep natural or cut slope used as a boundary feature, overlain in places by a low wall. Quarrying has disturbed a good portion of the western arc, and the overall impression is of something interrupted, worn down, and quietly retreating back into the field.

Within the interior, traces of a rectangular stone structure measuring around 9.3 metres by 6.4 metres survive alongside several mounds and hollows whose original purpose is not recorded. A fosse, that is, a defensive ditch, runs along the northern and eastern edges of the enclosure. There is a possible entrance at the north-northwest. Local tradition holds that a castle once stood within the enclosure, a detail that gives the site its name and adds a layer of intrigue that the visible remains alone would struggle to sustain. Whether this refers to a tower house, a more modest fortified structure, or simply a memory attached to the earthworks over generations, the record does not say. That ambiguity is itself characteristic of sites like this, where the written and the physical evidence are both fragmentary, and local knowledge fills the gaps in ways that are suggestive but difficult to verify.

The setting on a glacial ridge, a long low landform deposited by retreating ice, would have made this a practical location for a defended enclosure, offering elevation and clear sightlines across the surrounding grassland. The combination of a scarp boundary, a fosse, and interior structures points to a site that was once purposefully organised, even if time, quarrying, and weather have reduced it to something that rewards close attention more than it announces itself.