Known locally as ‘The Fort’, this ancient defensive site occupies the entire island, transforming what nature provided into a formidable stronghold. The fortification consists of a natural rock platform ingeniously incorporated into a defensive design, with a collapsed stone wall that weaves around and through the rocky outcrops. Where gaps appeared between the wall and platform, the builders meticulously packed them with small stones and clay, creating an unbroken defensive perimeter. From the interior, the wall appears deceptively low, but its construction from massive boulders with a core of smaller stones speaks to both its defensive purpose and the skill of its builders.

Within this stone enclosure, the remains of two rectangular structures tell of daily life in this isolated fortress. The larger building in the northeast section measures 7.5 metres externally north to south, with an internal space of 5.55 metres, whilst east to west it spans 5.7 metres externally and 4.55 metres internally. Adjoining its northwest corner, a second, more modest structure can be traced through the overgrowth, measuring approximately 5.6 metres externally north to south with 3.25 metres of internal space, and 5.4 metres externally east to west with 3.2 metres internally. These buildings likely once connected directly to the cashel wall, forming an integrated defensive and domestic complex.

The island’s strategic position becomes clear when you consider its accessibility; at low tide, a natural causeway connects it to the mainland, allowing defenders to control access whilst maintaining a retreat route. This type of coastal fortification, known as a cashel when built of stone, represents a common defensive strategy in medieval Ireland, where natural features were enhanced with human engineering to create nearly impregnable positions. The site was documented in the Archaeological Survey of County Donegal, compiled by Brian Lacey and his team in 1983, which catalogued field antiquities from the Mesolithic period through to the 17th century.