The oval mass of trees sits just half a metre above the water line, measuring roughly 23 metres east to west and 18 metres north to south, and is connected to the shore by a stretch of swampy ground. Beneath the vegetation and the eroding edges lies the remnant of a crannog, an artificial or partly artificial island dwelling of the kind built across Ireland and Scotland from the Bronze Age through to the early modern period, typically constructed from timber, stone, peat, and brushwood, and used as a defensible homestead on the water.

Lough Oony itself, a rectangular lake in County Monaghan running roughly 500 metres at its longest, appears in the historical record under its older name, Lough Uaithne. The Annals of Ulster, one of the major medieval Irish chronicle sources, mention it at several points between AD 719 and 1025. The final reference is stark: in 1025, the men of Fermanagh killed seventeen people on the lake shore. That entry suggests the lough sat within a contested and active landscape during the early medieval period, and the crannog would have been a feature of precisely that world. Two islands were recorded on the Ordnance Survey six-inch maps of 1834, indicating that the lake once held more open water than it does today. The southern of the two features is the one described here; a second crannog lies approximately 50 metres to the north. In 1983, two oak piles were identified at the site, and erosion of the perimeter exposed a construction matrix of small stones and brushwood matting, along with animal bones and fragments of charcoal, the quiet debris of domestic life from many centuries ago.