The site consists of a flat platform measuring approximately 41.5 metres northeast to southwest and 24.5 metres northwest to southeast, positioned strategically on a bend where a fast-flowing stream runs along its southern edge. What makes this location particularly intriguing is its defensive design; a wide, flat-bottomed fosse encircles the platform from west to north, measuring 7.7 metres across at the top and 4 metres at its base. This broad ditch likely served as a water-filled moat, working in concert with the natural protection offered by the stream to create an island-like defensive position.

Local tradition holds that this was once the site of an O’Boyle castle, home to one of the princes of this powerful Gaelic clan who ruled as chieftains of Boylagh. Writing in 1867, T. McGinley described how locals could still point out “the ruins of an old castle” on Strabrinna Hill, though the exact location had already become uncertain by that time. The connection to the O’Boyles is further strengthened by local folklore; one of the surrounding fields is still known as the ‘Soldiers Field’, suggesting a military presence that lingered in collective memory long after any structures disappeared.

While no masonry remains or evidence of buildings survive within the platform today, the earthwork may represent the remnants of a defensive bawn that once protected a castle or fortified residence. The eastern side shows no clear evidence of enclosure, though it’s possible the fosse was filled in over time along this section. Whether this was indeed the lost O’Boyle stronghold or another type of fortification, the site offers a glimpse into how medieval Irish lords used both natural features and human engineering to defend their territories in this rugged Donegal landscape.