In the south of County Galway, what was once Ballin Lough has been drained away entirely, and with it went the water that once defined three separate crannogs. A crannog is an artificial or partly artificial island, typically built during the early medieval period as a defended dwelling place, and the one recorded in the southern half of the former lake was no small structure. Ordnance Survey maps from 1838 and again from 1920 show it as an irregularly pear-shaped island, roughly 55 metres along its north-south axis and between 12 and 40 metres wide.

The antiquarian W. G. Wood-Martin visited the site and wrote about it in 1886, labelling it 'East Island' in his account. His excavation at the centre of the island turned up around 1.2 metres of peat, beneath which lay shell marl, a calcium-rich sediment common to Irish lakebeds. Further out, within a radius of roughly 3.7 metres, he found layers of small, flat stones placed in an irregular arrangement, the kind of deliberate stacking often associated with crannog construction. At the south-eastern shore, two wooden beams around 0.2 metres wide were also uncovered. It is a modest catalogue of finds, but enough to confirm that something was deliberately built here, and occupied long enough to leave material traces. Two further crannogs were recorded elsewhere within the same lake, suggesting the lough was once a site of some significance.

Today, the island is not visible at all. The drained lakebed has become a marshy area thick with reeds and scrub, and any surface trace of the crannog has been absorbed into the landscape. It exists now mainly on old maps and in Wood-Martin's careful, slightly dry prose, a structure that survived for perhaps a thousand years underwater only to disappear once the water was gone.