It sits roughly 35 metres from the southern shore, towards the eastern end of the lake, and to the casual eye it looks like a low, overgrown mound barely clearing the waterline. That is more or less what it is, but the mound is man-made, and it has been there for a very long time. This is a crannog, a type of artificial or partly artificial island dwelling common across Ireland and Scotland from the Bronze Age through to the early modern period, constructed from timber, stone, peat, and whatever else was to hand, and used as a place of habitation, refuge, or storage.

The structure at Knockaturly measures around 18 metres in diameter and rises only about 0.7 metres above the surface of the water. On its eastern side, where the water runs deep, timber piles are still visible beneath the surface, the skeletal remains of whatever platform or revetment once held the island together. The body of the crannog itself is composed of stones and charcoal mixed with animal bones, a matrix that suggests repeated occupation and domestic activity over an extended period. The lake that surrounds it has shrunk considerably since the nineteenth century. Ordnance Survey mapping from around 1834 recorded Knockaturly Lough at roughly 500 metres long and 180 metres wide; today those dimensions have contracted to approximately 420 metres by 130 metres, meaning the crannog now sits proportionally closer to the shoreline than it once did, and in shallower circumstances than its builders would have known.