Some sites are remarkable for what has vanished rather than what remains. Within the south-western sector of a rath near Drehid in County Kildare, there was once evidence of a souterrain, an underground stone-lined passage or chamber typically built during the early medieval period, used variously for storage, refuge, or both. By 1972, even that evidence was barely legible: a depression tracing along the inside of the rath's inner bank, which investigators at the time read as the probable line of such a feature running beneath the surface.

A rath, to use the term properly, is a circular earthen enclosure, the remains of a farmstead from early medieval Ireland, defined by one or more banks and ditches. The souterrain recorded here was never confirmed by excavation, only inferred from that slight ground-level irregularity. When the site was assessed, the interior of the rath was described as uneven and undulating, the kind of surface topography that hints at subsurface disturbance or buried structure. At some point after 1972, the land was levelled and put to pasture. Whatever that depression once suggested, it is no longer visible. The ground gives nothing away.