A crannog, to give it its proper name, is a man-made or heavily modified island dwelling, typically constructed during the early medieval period in Ireland, though some date much earlier and many continued in use into the seventeenth century. This particular example sat at the south-western end of Ballin Lough until the lake itself was drained, leaving the site marooned in a landscape that has quietly swallowed it.

When the antiquarian W. G. Wood-Martin investigated the site, which he recorded in 1886 as 'Middle Island', it was still visible as a small, roughly triangular island on Ordnance Survey maps from both 1838 and 1929. His excavation near the western edge revealed a careful layering of occupation and construction. The uppermost deposits held peat and clay with scattered bones. Below that came a more telling assemblage: wood ash, quantities of unbroken cherry stones, cracked hazel nuts, broken animal bones and teeth, and a ball of red colouring matter, all compressed into a layer roughly 0.8 metres deep. Deeper still was a floor of basket or wickerwork construction, made from hazel rods, a material both flexible and locally abundant. Beneath this floor lay a series of sawn oak beams, each approximately 15 metres in length, running north to south and fastened at regular intervals with pairs of dowels, with ash poles used to secure them further. The precision of the joinery suggests this was no improvised platform; it was engineered. A stratum of peat lay below even the beams. Two further crannogs are recorded as having occupied the same lake, which gives some sense of how significant Ballin Lough once was as a place of settlement or refuge.

Today the site offers very little to see. The island is no longer discernible as such, absorbed into a densely vegetated marshy area. Its value is less in the visiting than in what the excavation retrieved, a detailed cross-section of a vanished lake dwelling, complete with food remains, construction materials, and a pigment whose purpose remains unexplained.