A souterrain once lay beneath this ground: a souterrain being an underground stone-built passage or chamber, typically constructed during the early medieval period and associated with nearby settlement, used variously for storage, refuge, or purposes that archaeologists still debate. It never made it onto Ordnance Survey maps, and at some point in the 1950s, on the basis of local information, it was simply filled in. No surface trace remains.

The loss is quiet but telling. Souterrains are rarely dramatic features even when intact, being subterranean by nature, but they carry considerable archaeological value as indicators of early settlement patterns and land use. The Iveragh Peninsula, on which Carhoobeg sits, is particularly dense with early medieval and prehistoric remains, and a souterrain in this location, close to the Laune, would have fitted a recognisable pattern of habitation along fertile riverside ground. That this one went unrecorded on official maps, and was filled in within living memory, places it in a category that archaeological surveys sometimes have to acknowledge honestly: the site that survives only as an absence, known through local recollection rather than any physical evidence.