Today there is nothing to see at the surface, which makes the nineteenth-century descriptions of this place all the more striking by contrast.

A souterrain is a man-made underground structure, typically stone-lined, built during the early medieval period and associated with the raths, or ringforts, that dot the Irish countryside. These earthen enclosures were farmsteads of the early medieval period, and their souterrains served variously as storage spaces, refuges, or both. The souterrain at Clashnagarrane was recorded in the 1840s under the name 'Clashnagurraun Cavern', and whoever documented it noted that it was 'very spacious, having several apartments', with its entrance located 'in the centre of the Fort'. That is a more elaborate arrangement than many souterrains, which tend to be simple narrow passages. The site appeared on the 1846 Ordnance Survey six-inch map simply as 'Cave', a label that suggests local awareness of the feature even if its precise character was not fully understood. At some point between that mapping and the present, the structure either collapsed or was filled in, and no visible remains survive.