It does not look like much at first glance, but where the turf has worn away, the ground reveals itself: small, angular fragments of sandstone packed into soil black with charcoal. This is a burnt mound, a type of prehistoric feature found across Ireland and Britain, generally interpreted as the debris left by repeated episodes of heating stones in fire and plunging them into water-filled troughs, likely for cooking, bathing, or industrial processes whose exact purpose is still debated. The mound at Cullentragh is the accumulated waste of that activity, the cracked and spent stones discarded into a heap over what may have been generations of use.

The mound measures roughly 13.9 metres north to south and about 12 metres east to west, forming a shallow arc of comparatively firm, dry ground in an otherwise waterlogged margin at the base of a north-east-facing ridge slope. It appears to have been partly levelled at some point, and the eastern side has slumped. A surface scatter of stone and charcoal extends a further ten metres or so to the south-east, suggesting either the original mound was larger or material was spread beyond its main body over time. The exact edges are difficult to determine. A second burnt mound lies on the same shoreline, roughly 60 metres to the south-east, which hints that this stretch of lakeshore was a place people returned to repeatedly. The surrounding landscape adds to that impression: an 1838 map records the possible outlines of two crannógs, the artificial or semi-artificial island dwellings used from the Bronze Age through the early medieval period, within Derrykin Lough itself, one close to this mound and another about 70 metres to the south-west. A rath, a circular earthwork enclosure associated with early medieval settlement, sits roughly 140 metres to the west-north-west. Whether any of these features were contemporary with one another is unclear, but taken together they suggest a place that drew people across a long stretch of time, and for varied reasons.