This isn't a natural island at all, but rather a crannog; an artificial island created by piling stones on the lakebed. These structures were once common throughout Ireland and Scotland, typically built during the early medieval period as defensive homesteads for local families.

The crannog's construction shows careful planning, with loose stones arranged around the island's perimeter that were deliberately built up to create a proper wall face on the inner side. This would have provided both structural support and a defensive barrier for whatever dwelling once stood at the centre. A two-metre gap in this stone boundary on the northeast side might be a later modification, though it's difficult to say for certain without further investigation.

Crannogs like this one at Moyle were ingenious solutions to the challenges of medieval life in Ireland. The water provided natural protection from raiders and wild animals, whilst the artificial island offered a stable platform for building. Many crannogs were accessed by causeway or boat, and some remained occupied well into the 17th century. This particular example, documented in the Archaeological Survey of County Donegal, represents one of many such structures that dot the lakes of Ulster, each one a testament to the resourcefulness of Ireland's medieval inhabitants.