It looks unremarkable from the shore, the kind of growth you might easily dismiss as a natural accident. What it marks, however, is a submerged artificial island, a crannog, sitting just beneath the lake's surface and largely out of reach.

Crannogs are man-made lake dwellings, typically constructed from timber, stone, peat, and brushwood, and they were used in Ireland from the Bronze Age through to the early medieval period, sometimes later. This one at Corran is an oval earthen mound, roughly eleven metres north to south and seven metres east to west, rising to about 1.8 metres in height. Its flat top lies under approximately 0.3 metres of water. What makes it particularly vivid as an archaeological object is what survives below the waterline: timbers protruding intermittently from the almost vertical sides of the mound, a concentration of stones at its south-western base, and the remnants of tree stumps at the north-east and south-east edges of the surface. The lake floor drops away from the base of the mound gradually, reaching a depth of around six metres. Because the site was inaccessible at the time of survey, the physical description was pieced together from local knowledge provided by two individuals, John Kearney and Patrick Cleary, whose observations from the lakeshore and presumably by boat gave the record much of its detail.

The crannog is visible from the shore, just about, if you know to look for the rushes growing from its waterlogged surface. The surrounding low hills keep the lake quiet and relatively enclosed, which gives the site an undisturbed quality. The exposed timbers and the submerged structure mean this is a place better observed than approached; the water is shallow enough over the mound itself, but the archaeology beneath is fragile, and the site has clearly survived in part because of how difficult it is to reach.