Whilst the Ordnance Survey maps from the 19th century mark it as a ‘Fort’, no physical traces of traditional fortifications remain visible today. The island, connected to the mainland by a causeway, holds only subtle clues to its ancient past; local tradition speaks of stones being systematically removed from the site over the years, gradually erasing what once stood here.

Archaeological surveys suggest this wasn’t a fort in the conventional military sense, but rather an island cashel; a type of stone enclosure that served as a defended homestead during Ireland’s early medieval period. These structures typically consisted of circular stone walls surrounding domestic buildings, providing both protection and status for their inhabitants. The comparison to a similar site at Doon Lough helps paint a picture of what might have existed here: a substantial stone settlement, strategically positioned on an island for natural defence.

The removal of stones mentioned in local folklore was likely for practical purposes; dressed stones from ancient sites often found their way into nearby field walls, houses, and farm buildings throughout the 18th and 19th centuries. This common practice of stone robbing has left many of Ireland’s archaeological sites as mere shadows of their former selves, with Rough Island’s cashel being another casualty of this widespread recycling of building materials. Today, visitors to the island must use their imagination to reconstruct the settlement that once commanded this watery stronghold in the Donegal landscape.