What is now easy to overlook beside Kimmage crossroads was, for centuries, the artery that kept Dublin alive, and the cartographers of two very different eras thought it important enough to name explicitly: the 1837 Ordnance Survey six-inch map labels it the 'City Watercourse', while the Down Survey maps of 1655 to 1656 describe it simply, and rather grandly, as the 'water that supplieth Dublin'.

The Down Survey, carried out under William Petty in the mid-seventeenth century, was one of the most ambitious land-mapping exercises in Irish history, produced largely to facilitate the redistribution of land following the Cromwellian settlement. That its surveyors paused to note this particular channel speaks to how central it remained to the city even at that late date. The watercourse is medieval in origin, and this surviving section runs from Kimmage crossroads to a point known as the Tongue, also at Kimmage. Midway along this stretch, the channel is joined by the Poddle, a river whose name will be familiar to anyone who has looked into Dublin's early topography. The two flows travel together briefly before separating again at the Tongue, a fork whose name describes precisely what happens there. The detail is recorded by both Joyce in 1912 and Berry in 1891, drawing on earlier documentary sources.

The area sits within the kind of dense residential landscape that makes it easy to walk past without registering what lies beneath the surface. There are no grand markers or interpretive signs to announce the watercourse's significance. Anyone interested in tracing this fragment of medieval infrastructure would do well to consult a georeferenced version of the 1837 OS six-inch map alongside a modern street map, which allows the line of the channel to be followed in relation to current roads. The Poddle itself, much of whose length now runs underground through the city, briefly surfaces in this part of south Dublin, and the confluence and separation at the Tongue is the kind of quiet geographical curiosity that rewards a slow, attentive walk rather than a hurried one.