Outside St. James Gate, one of the old entry points into medieval Dublin, a mill once turned using water drawn away from the city's own watercourse, and yet its exact position on the ground has never been firmly established. The gate itself stood at the western edge of the old city, and the area beyond it was long a zone of industry and activity, but this particular structure exists now only as a line in the historical record.

The evidence for the mill comes from Howard Clarke's work on medieval Dublin, published in 2002, which places it outside St. James Gate and notes that it relied on water diverted from the city watercourse. That watercourse was a managed channel that carried water into and around Dublin, serving both practical and commercial needs. Diverting such a supply to power a mill was a common enough arrangement in medieval Irish towns, where watermills, which use flowing or diverted water to drive a grinding wheel, were among the more significant pieces of infrastructure a community could possess. The fact that this one drew from a civic water supply rather than a natural stream suggests it had some kind of formal or semi-official standing, though the records do not go further than that.

Because the site has not been precisely located, there is no specific spot to visit or mark to look for. The broader St. James Gate area in Dublin's south city has changed enormously over the centuries, most visibly through the expansion of the Guinness brewery, which has occupied and reshaped much of this district since the eighteenth century. Anyone with an interest in the medieval layers beneath the modern city might find it worth reading Clarke's wider work on Dublin's urban geography, which places this mill within a fuller picture of how the city's edges were organised and used. The absence of a fixed location is itself part of what makes this entry interesting: it is a reminder of how much urban infrastructure simply did not survive into the documentary or archaeological record in any recoverable form.