That situation, equal parts frustrating and quietly fascinating, is the central fact of a souterrain recorded at Stradbally North, on grounds that once belonged to Castleoaks House Hotel beside the River Shannon. Souterrains are underground chambers or tunnels, typically built during the early medieval period in Ireland, constructed using corbelling, a technique where stones are layered inward and upward to form a roof without mortar. They are thought to have served as places of refuge, storage, or both. This particular example had the additional distinction of never appearing on Ordnance Survey historic mapping at all, meaning it existed entirely outside the official record until the ground gave it away.

The opening was discovered around 1987, when the site was still in agricultural use as pasture. What was found was an entrance to a subsurface corbelled passage running westward, with the Shannon visible in that same direction. The precise extent of the tunnel was not established before the land use changed. By 2000, when O'Rahilly documented the site, the field had already been converted into a pitch and putt course, and the exact position of the underground passage had been lost. Development pressure continued: the site was assessed in 2001 as part of a proposed residential and hotel suite scheme by Byrne, and two phases of pre-development testing followed in 2002, along with a monitoring brief in 2003, all carried out by Collins. None of that work turned up anything of archaeological significance, which may reflect the limits of the testing as much as anything else. Aerial photography taken between 2011 and 2013 showed that the area had since been built over as a housing estate.

There is, in practical terms, very little for a visitor to see here now. The Castleoaks House Hotel grounds on the southern bank of the Shannon in Stradbally North are the general area of interest, but no surface trace of the souterrain is known to survive, and the housing development that covers the site is not accessible for casual exploration. What remains is the record itself, and the unresolved question of whether the corbelled passage is still intact below the foundations, undisturbed and unlocated, waiting for some future circumstance to bring it back to light.