It measures roughly ten metres across and rises about a metre above the waterline, which does not sound like much until you consider what it probably is: a crannog, an artificial or partially artificial island constructed in a lake, used in Ireland from the Bronze Age through to the early modern period as a defended dwelling place. This one is technically attached to the south-eastern shore, making it more of a promontory than a true island, but the distinction mattered less in practice than the water and the reeds that surrounded it.

What makes the site quietly interesting is the way it has shifted in appearance between two Ordnance Survey mappings. On the 1834 six-inch edition, it appears as a narrow peninsula extending from the shore into the lake. By the 1907 edition, it is recorded as a broader promontory, suggesting either that the land connection had widened over the intervening decades, perhaps through natural accumulation of sediment and vegetation, or that earlier surveyors simply had less detail to work with. Cordoo Lough itself sits among drumlins, the smooth oval hills shaped by glacial drift that give this part of Monaghan its rolling, enclosed quality. The lake is sub-rectangular, running roughly four to five hundred metres on its longer axis, and the crannog occupies a sheltered corner of its south-eastern edge.

Access, in any practical sense, is not straightforward. The dense reed growth surrounding the mound has previously made it impossible to reach on foot, meaning the grass-covered cairn at its centre has never been properly examined up close. That inaccessibility is itself part of the record, a small artificial island that has outlasted the people who built it largely because the wetland around it has kept curiosity at bay.