By the time archaeologists returned a decade later, even the outline of the structure had largely vanished, leaving only a shallow, stone-filled depression in the ground.

The feature sits at the centre of a rath, a type of enclosed farmstead typically defined by one or more circular earthen banks, common across Ireland from the early medieval period. Inside that enclosure, a souterrain had been constructed, an underground stone-lined passage or chamber often associated with storage, refuge, or both. When it was first inspected in July 1982, the souterrain appeared to be T-shaped in plan, with its main passage oriented roughly north-northeast to south-southwest. A single roof lintel survived to give some sense of the original construction: 0.9 metres long, 0.9 metres wide, and 0.3 metres high. That modest slab was one of the few measurable facts the site still had to offer. When surveyors came back in May 1992, the T-shaped plan was no longer legible. The stone-filled hollow that remained was barely enough to confirm something had once been there at all.

What makes the site quietly compelling is the speed of that erasure. A decade separated two visits, and between them a structured underground feature became an ambiguous dip in the earth. The rath itself presumably still marks the landscape at Rathwilladoon, but the souterrain it once contained has effectively disappeared back into it.