This modest archaeological site, measuring approximately 20 metres across, consists of a ruined stone wall that once stood between 85 centimetres and a metre wide. The wall survives best on the western side, where visitors can still make out the original construction that would have completely enclosed the circular space within. The fort sits amongst light-soiled pasture dotted with rocky outcrops, a typical landscape feature of this part of Ireland.

The interior of the cashel contains scattered stones, though these don’t form any recognisable pattern that might hint at internal structures or buildings. This type of ringfort, built entirely of stone rather than earth, is known as a cashel and would typically have served as a defended farmstead during the early medieval period. However, the name ‘Altar Fort’ suggests a rather different chapter in its long history; local tradition holds that the site may have been used during the Penal Laws era, when Catholic worship was severely restricted and Mass had to be celebrated in secret outdoor locations.

The site appeared on the Ordnance Survey 6-inch maps during their second and third editions, marking it as a recognised feature of the local landscape worth documenting. Today, it stands as one of many such monuments recorded in the Archaeological Survey of County Donegal, a comprehensive catalogue of the county’s field antiquities spanning from the Mesolithic period through to the 17th century. While it may not be the most spectacular of Donegal’s ancient sites, Altar Fort offers a tangible connection to both Ireland’s early medieval past and its more recent history of religious persecution and resilience.