In the case of a dwelling recorded in the Dundrum area of County Dublin, that is precisely the situation. What we know amounts to a single depiction on a seventeenth-century survey, enough to confirm that something stood here, but not enough to say exactly where.

The evidence comes from the Down Survey, carried out between 1655 and 1656 under the direction of William Petty. It was among the most ambitious cartographic projects undertaken in Ireland up to that point, commissioned by the Cromwellian administration to map confiscated lands in enough detail to redistribute them among soldiers and creditors. The surveyors recorded not just townland boundaries and land quality but also visible structures, and somewhere in the Dundrum area they noted a dwelling. Whether it was a modest farmhouse, a more substantial residence, or something in between, the survey does not make clear. The notation places it broadly within the locality, but the precise plot has not been identified, and no later documentary or archaeological work appears to have pinned it down further.

For anyone interested in following up, Dundrum today is a busy south Dublin suburb, and much of its earlier landscape has been built over across successive centuries. The Down Survey maps themselves are accessible online through the Down Survey of Ireland project, hosted by Trinity College Dublin, which has digitised and georeferenced the original barony and parish maps. Comparing the seventeenth-century depiction against modern mapping gives a rough sense of the area in question, though the uncertainty about the dwelling's precise location means that no particular spot on the ground can be pointed to with confidence. The interest here lies less in visiting a site than in the act of looking at the map itself, and sitting with the fact that even a relatively recent and well-documented survey can leave a building adrift in a landscape, present but unplaceable.