At some point in the past, a stone was dislodged during agricultural work, opening up a chamber that had been sealed from view for an unknown period of time. The structure uncovered was a souterrain, an underground passage or series of chambers typically constructed during the early medieval period in Ireland, often associated with nearby settlement sites and used variously for storage, refuge, or both.

What local accounts recalled of the interior was modest but telling. One side of the main chamber had been stone-built, while the other was simply earth-cut, a combination that was not unusual in souterrain construction and suggests the builders adapted to whatever material and ground conditions were available. Off the main chamber there was a smaller secondary chamber, and a set of steps was also remembered by those who had seen the interior. The asymmetry of the construction and the presence of steps hint at a structure with some deliberate design, even if the full extent of it remains unknown. Today there is nothing visible above ground at Caherdesert to indicate any of this. Whatever was exposed during ploughing has since been covered over or lost, and the site leaves no surface trace.