It is easy to walk past without registering what it represents: the physical remnant of a working mill that was already old enough to be recorded in a seventeenth-century government survey. The channel is a millrace, a constructed watercourse designed to direct river flow onto a mill wheel with enough force and volume to drive the grinding machinery. This one runs off the Hurley River, and what remains of it sits on the boundary between Borranstown and Ballymadun in north County Dublin.

The paper trail for this mill reaches back to the Civil Survey of 1654 to 1656, a comprehensive Cromwellian-era land record compiled to establish ownership across Ireland following the upheavals of the 1640s. That survey, as cited by Simington in 1945, lists a mill at a place recorded as Balmadun, which corresponds to the present-day townland of Ballymadun. A century later, the cartographer John Rocque marked a structure labelled Ballymadun mill on his detailed map of County Dublin, published in 1756. Whether the mill operating in Rocque's time was the same building noted in the Civil Survey, or a later construction on the same site, is not certain, but the continuity of name and location across both sources suggests a long-established milling presence on the Hurley River at this point.

The surviving millrace is the most tangible element remaining. It follows the townland boundary between Borranstown and Ballymadun, and the stone lining is what makes it identifiable as a deliberate construction rather than a natural watercourse. Visitors interested in seeking it out should be prepared for the fact that this is not a managed or signposted heritage site; it is a field-edge feature in an agricultural landscape. The boundary between the two townlands can be traced on older Ordnance Survey maps, which remain useful for orientating yourself in an area where the mill itself has long since disappeared. The Hurley River is a modest stream, and the millrace is correspondingly modest in scale, but the stone lining, where it survives, gives a clear sense of the engineering involved in redirecting water to serve an agricultural community that depended on milled grain as a basic necessity.