No trace of it survives today, yet the documentary record is unusually persistent, suggesting a structure that was genuinely significant to the community that depended on it. Water mills of this kind, which harnessed a river's current to drive millstones for grinding grain, were among the most economically vital buildings in any medieval settlement, and the one at Rathfarnham was no exception.

The earliest surviving cartographic evidence comes from the Down Survey, the ambitious land mapping project carried out between 1655 and 1656 under William Petty, which recorded land ownership across Ireland in the aftermath of the Cromwellian conquest. That survey shows a mill on the eastern bank of the Dodder at Rathfarnham, placing it firmly within the landscape of mid-seventeenth-century Dublin. By 1837, when the Ordnance Survey produced its six-inch mapping of Ireland, the structure was already being referred to as the 'Old Mill', suggesting it was no longer in active use and had perhaps already fallen into decline. Historian Rob Goodbody has noted that the mill was well documented in medieval sources, which points to origins considerably earlier than the Down Survey record. The building that appeared on the 1837 map was most likely the same site, or its direct successor, and it was demolished sometime in the latter part of the nineteenth century.

Because the mill no longer exists, there is nothing physical to seek out at the site. The eastern bank of the Dodder at Rathfarnham is the general area to orient yourself, though the precise footprint of the building is not marked or memorialised in any way. What the site offers instead is a particular kind of historical layering, a place where maps from three different centuries each register the same structure in different states of life and decay. The Down Survey maps are freely accessible online through Trinity College Dublin, and comparing them against the 1837 Ordnance Survey sheets, also available digitally, gives a reasonable sense of how the mill sat within the wider Rathfarnham townscape before it was lost.