The evidence for the building comes from two remarkable mid-17th century sources. The Down Survey, carried out between 1655 and 1656 under the direction of William Petty, was one of the first large-scale cadastral mapping projects in the world, produced to facilitate the redistribution of Irish land following the Cromwellian conquest. Its map marks a dwelling near the location later associated with Harristown House. The Civil Survey, compiled around the same period between 1654 and 1656, is more blunt in its assessment: by that point the structure had already been reduced to what it describes as the "ruins of old walls of stone" (Simington, 1945). Harristown House is thought to have occupied this same site, though by the time surveyors were recording it, the building had already passed into decay. What stood there before the ruin, and who built it, is not recorded in the surviving notes.

Today the site falls within the grounds of Dublin Airport, subsumed into the infrastructure of the runway. There is nothing to see at ground level, no marker, no remnant, and no practical means of access for a visitor. The interest here is less about standing in a place and more about the particular strangeness of knowing that a documented medieval or early modern structure exists in permanent suspension beneath one of the most heavily trafficked surfaces in the country. For anyone drawn to the archaeology of buried and erased landscapes, the detail survives in Geraldine Stout's compiled record, and the original Civil Survey entry can be traced through Simington's 1945 publication. The layers are there, even if the ground above them belongs entirely to the present.