It grows from what appears to be a small mound in the water, and if you did not know what lay beneath it, you might not look twice. What lies beneath is a crannog, an artificial or partly artificial island of the kind built throughout Ireland and Scotland from the Bronze Age well into the early medieval period, typically as a defended dwelling place. When inspected in 1988, this one was almost entirely submerged, its presence announced only by that solitary bush rising from the surface.

The structure itself is about eleven metres in diameter, built around a conical stone core with timbers incorporated into it, and bounded by a ring of stakes, some of which were still protruding above the waterline at the time of inspection. Extending southward from the main mass is a wooden platform, constructed from large timbers laid horizontally over a base of stones, which would have served as a landing stage or working area. The edge of the crannog drops away steeply, a detail that speaks to deliberate construction rather than gradual accumulation. What makes the site stranger still is that it does not sit alone. Another crannog lies roughly sixty metres to the east, and a third approximately one hundred metres to the west, meaning that Ballymore Lough once supported at least three of these structures within a relatively compact stretch of water. The clustering of crannogs on a single lake is not unheard of in Ireland, but it is unusual enough to suggest the lough held particular importance for the communities who built and occupied them.