Not destroyed in any recorded dramatic fashion, not built over with a fanfare of documentation, simply lost, its location reduced to a single scholarly note and an absence on the map. That ambiguity is itself a kind of historical curiosity, a reminder that the fabric of a medieval city was far denser and more varied than the landmarks that survive it.

What little is known comes from historian H.B. Clarke, who notes in his 2002 work that St John's mills lay within the precinct of St John the Baptist's Hospital during the fifteenth century. The hospital itself was a medieval charitable institution, the kind of foundation, part religious house, part hospice, that was common across European towns in the later Middle Ages, typically run by a religious order and funded through rents, donations, and the revenues of attached properties. Mills were frequently among those revenue-generating assets. A working mill, whether grinding grain or fulling cloth, could produce a reliable income that helped sustain the hospital's charitable and religious functions. The connection between ecclesiastical precincts and milling was entirely ordinary in this period, which makes it all the more frustrating that the precise location of these particular mills has not been pinned down.

For anyone drawn to this kind of gap in the historical record, the south city area around where St John the Baptist's Hospital once stood is worth approaching with Clarke's 2002 volume, or through the published maps and records held at Dublin City Library and Archive on Pearse Street. The Mills are not precisely located, as the sources note plainly, so there is nothing to stand beside or photograph. What the site offers instead is the slightly vertiginous experience of looking at an ordinary urban streetscape and knowing that something functional and significant once operated here, probably somewhere close, recorded only in a passing reference and otherwise entirely gone.