The mound is roughly square, measuring just under nineteen metres in both directions, and is defined by a scarp, a slight but deliberate drop in ground level around its edges, still about half a metre high. To the east and west, a wide shallow fosse, essentially a defensive ditch, traces the outline of what was once a more clearly bounded space. A few stones are still partially visible at the north-east corner. That is more or less all there is to see.

What makes Kilbeg quietly interesting is what those modest earthworks once carried. A castle stood on this mound, though no above-ground trace of it survives today. The combination of a raised platform and surrounding fosse is consistent with the kind of fortified residence common across medieval Ireland, where a mound, whether natural or artificially constructed, provided both a defensive elevation and a visible statement of local authority. The castle here has been assigned its own archaeological record, but it exists now only as an absence, a structure fully consumed by time, collapse, or later stone-robbing, leaving behind nothing but the shaped ground beneath it. The mound itself, in a way, is the more durable monument.