That last detail is the quietly unsettling part. When archaeologists first documented it in March 1983, the souterrain was measurable and mappable: the first chamber ran east to west at 7.8 metres long and two metres wide, the second angled away to the north-north-east at 4.4 metres long and 1.4 metres wide, with a blocked-up creep, a low crawl-through opening between sections, still visible in the western wall of the first chamber. When the same site was revisited in October 2001, no surface trace of the structure remained at all.

A souterrain is a deliberately constructed underground passage or chamber, typically built during the early medieval period in Ireland, usually of drystonemasonry, and associated with nearby settlement enclosures. They are thought to have served as places of refuge, cool storage for dairy produce, or both. This one sat within a cashel, a type of stone-walled ringfort enclosure, the remains of which are recorded separately for the Cartron townland. The drystone construction method, in which stones are laid without mortar and rely entirely on their own weight and careful placement for stability, makes souterrains both durable over centuries and vulnerable to collapse or deliberate infilling once no one is actively maintaining them. The reference to McCaffrey's 1952 survey suggests the site had already attracted scholarly attention before the 1983 inspection confirmed its dimensions and layout.

The disappearance of visible surface traces between 1983 and 2001 is not unusual for this class of monument. Agricultural activity, ground settlement, or simple collapse of the roof into the passage can erase what had previously been detectable as a depression or a slight irregularity in the soil. The structure itself may still be largely intact underground, or it may not. Either way, the cashel enclosure it belonged to remains the more likely thing to look for on the ground at Cartron, though the souterrain beneath it has its own particular quality of absence.