A millrace is simply the channel cut to direct water from a river to a mill wheel, and in this case the water came from the Dodder, carried south-westward to power a mill that has long since vanished from the landscape. What survives is a cartographic ghost: a map attached to a lease dated 1701 that shows the mill sitting immediately to the south of Donnybrook Castle, its watercourse traced in careful lines toward the river.

The 1701 lease map is the primary evidence for the mill's existence and position. It places the structure in close relation to Donnybrook Castle, a pairing that would have been entirely typical for the period, when mills were essential economic assets attached to landed estates and managed as part of their working infrastructure. The millrace running south-west to the Dodder suggests a well-considered piece of engineering, drawing on the river's reliable flow. According to local researcher Danny Parkinson, the probable site of the mill corresponds to the present grounds of the Sisters of Charity in Donnybrook West, where a grotto now occupies part of the land. The religious community that eventually came to hold these grounds would have had little use for milling infrastructure, and it is not unusual for such industrial traces to disappear entirely once their original purpose lapses.

The Sisters of Charity grounds are not generally open to casual visitors, so direct inspection of the likely mill site is not straightforward. The grotto that now marks the approximate location is a relatively modern religious feature rather than any remnant of the mill itself. For those interested in following up the documentary evidence, the 1701 lease map is the most concrete starting point, and the Dodder riverbank in this stretch of south Dublin still rewards attention; the river's course and character here have shaped settlement patterns for centuries. Anyone researching the industrial or estate history of the Donnybrook area will find the mill's brief appearance on that early map a useful, if frustratingly incomplete, trace of what the landscape once held.