Measuring roughly eleven metres east to west and only three and a half metres north to south, it is less a natural landmass than a constructed one, built up by human hands at some point in the past and now so thoroughly colonised by vegetation that its artificial character is easy to miss entirely.

This is a crannog, a type of artificial or semi-artificial island settlement found throughout Ireland and Scotland, typically built out into lakes or wetlands using layers of timber, peat, brushwood, and stone. They were used from the Bronze Age well into the early medieval period, serving as defended homesteads whose watery surroundings provided a degree of natural protection. What makes this particular example slightly unusual is that it appears to have been constructed on top of a natural reef, meaning its builders took advantage of an existing geological feature rather than starting entirely from scratch. Lough Rea contains at least five other crannogs in the same general area of the lake, suggesting the lough was once a site of considerable activity, with communities repeatedly choosing this form of island dwelling across what may have been a very long stretch of time.