Promontory fort - inland, Fawnlion, Co. Leitrim

The example at Fawnlion in County Leitrim applies the same logic to the interior of the country, exploiting a plug of rock outcrop that rises from a south-facing slope as though it were a cliff-girt peninsula thrust into the surrounding farmland. The result is a triangular, grass-covered enclosure roughly forty metres along its longest axis, ringed on most sides by natural cliffs between two and six metres high, and needing artificial intervention only at its narrowest point to the north-east.

At that vulnerable north-eastern end, whoever built this place dug a fosse, the term for a defensive ditch, cutting a trench roughly ten metres long, eight metres wide at the top and narrowing to three and a half metres at the base, with an internal depth of around two and a half metres. The effort required to excavate that in rock-studded Leitrim ground was considerable, and it underlines how seriously the site's builders took the one direction from which the natural terrain offered no protection. Inside the enclosure, a further rectangular platform, measuring thirteen by seven metres, is itself defined by a shallower fosse on three sides, with its north-western edge hard against the cliff. This inner feature may represent a more sheltered or elevated working area within the fort, set apart from the rest of the enclosure. Later generations have left their own mark: stone field walls have been built along the perimeter of the promontory, reusing its edges for agricultural boundary-making and layering a more recent, pastoral logic over whatever purposes the original builders had in mind. Michael J. Moore's Archaeological Inventory of County Leitrim, published in 2003, provides the detailed survey measurements on which the understanding of this site rests.