In north County Tipperary, a field once associated with a long-vanished building called Derry House was formally listed as a possible castle site in 1992 and again in 1998. The catch is that no evidence of a castle has ever been found there, no surface trace, no cartographic record, and nothing in the documentary sources to suggest one ever existed.

What the historical maps do record is the house itself, a modest but intriguing structure. The first edition Ordnance Survey six-inch map shows Derry House standing, and by the 1843 edition the same map has quietly updated its label to read simply "site of Derry Ho.", meaning the building was already gone within living memory of the surveyors. The Ordnance Survey Name Books of around 1840 refer to it as "Derry old House", a description that hints the structure may have dated to the seventeenth century. The surveyors also noted something more specific: the house had been "raised to the foundation", meaning it was demolished or had collapsed to its base, and that it had last been occupied roughly twenty years before they visited, by a woman recorded only as a widow Whalen. The 1654 to 1657 Down Survey, one of the most comprehensive mappings of Irish land carried out after the Cromwellian settlement, shows nothing resembling a castle in the vicinity either. The castle classification appears to have been a cautious, speculative entry rather than a conclusion drawn from any real evidence, and it has not been borne out by subsequent investigation.

What remains at the location today is essentially nothing visible, a site where a house once stood, itself probably a modest seventeenth-century structure, and before that, apparently, nothing of the fortified kind at all. The interest lies less in what is there than in how a place accrues historical weight through bureaucratic caution and the slow accumulation of map annotations, each generation of record-keepers inheriting and questioning the assumptions of the last.