This substantial circular structure, measuring 95 metres across its interior, consists of a collapsed stone wall that once fully enclosed the hilltop site. Over the centuries, practical farmers have repurposed many of the fallen stones, incorporating them into sheep folds built against the original wall; a common fate for ancient monuments across the Irish countryside.

The enclosure’s interior reveals numerous rock outcrops scattered throughout, with particularly prominent formations flanking what appears to have been the original entrance, a gap in the northwestern section of the wall. Its strategic position is no accident; from this vantage point above the boggy hillside, those who built it could monitor movement through the Barnesmore Gap below, one of the region’s most important historical passage routes through the mountains of Donegal.

First recorded on the 1906 Ordnance Survey maps as ‘Cashelnabean’, the site’s name derives from the Irish ‘caiseal’, meaning stone fort or enclosure. While its exact age and purpose remain uncertain, hilltop enclosures like this one typically date from the Iron Age through to the early medieval period, serving variously as defensive structures, livestock enclosures, or centres of local power. Today, it stands as a weathered but enduring testament to the communities who once commanded these hills, their stones now sheltering sheep rather than people.