A cashel is a stone-walled ringfort, a type of enclosed farmstead common across early medieval Ireland, and within the southern portion of the one at Caherhenryhoe there are signs of a souterrain: an underground stone-lined passage or chamber, typically constructed during the early medieval period and used for storage or as a place of refuge. The evidence is there if you know what to look for, an east-west alignment of what appears to be a stone wall, and a scatter of flat slabs that may once have served as roof lintels before they collapsed inward.

The difficulty is that the site has been used as a dumping ground for field-clearance rubble, the accumulated stone shifted off surrounding land over generations of agricultural tidying. That kind of disposal was, and remains, entirely practical from a farming perspective, but it has the effect of obscuring precisely the features that would allow any confident assessment. What lies beneath is uncertain. The wall line and the fallen slabs are suggestive enough to register the site as a possible souterrain, but the rubble makes it impossible to say much more without intervention. The cashel itself, a separate monument within the same complex, gives the broader context: this was once an enclosed settlement, and souterrains are frequently found within or immediately adjacent to such enclosures across Connacht and beyond.