This rectangular stone fortification, measuring roughly 36 metres east to west and 27 metres north to south, exists today as little more than a collapsed bank of stones rising less than a metre at its highest point. First documented in detail during the 1942;43 survey by O'Kelly, the site presents itself as a puzzle for archaeologists and historians alike; whilst its stone construction is evident throughout the remaining earthworks, no original facing stones remain visible, and even the location of its entrance has been lost to time.

The fort's historical significance may extend beyond its physical remains. Local historian Bosco Ryan has suggested an intriguing connection between this earthwork and the mysterious Knockmonihy Castle, a structure that appears on the Down Survey maps from 1654;57. These maps, created during Cromwell's redistribution of Irish lands, show a castle symbol east of Knockmuinaha, precisely where Barnanenagh Fort stands today. If this theory proves correct, the humble earthwork visible on modern aerial photographs could represent the last traces of a once;significant defensive structure from Ireland's tumultuous medieval period.

Today, whilst the site may not impress casual visitors with grand walls or towers, it offers something perhaps more valuable: a tangible link to the layers of history that have shaped the Irish landscape. The fort's poor preservation actually adds to its archaeological interest, as it represents the countless defensive sites across Ireland that have gradually melted back into the earth, their stones repurposed for field walls and farm buildings over the centuries. Recent digital imaging has helped archaeologists better understand the site's layout, ensuring that even as the physical structure continues to deteriorate, its footprint remains recorded for future generations to study.