Known as the Glib Water, this channel was not a river in any natural sense but a managed overflow, a working piece of civic infrastructure threading its way outside the town walls at the north-west corner of Dublin's medieval defences. What makes the discovery quietly remarkable is that the channel survived long enough, and in enough forms, to leave legible traces across several centuries, from organic timber to fired brick.

An archaeological assessment carried out in 1997 under licence No. 97E0061, directed by C. Walsh and submitted to the National Monuments Service, uncovered evidence of the Glib Water dating to at least the 15th century. The site sits in an area associated with the medieval Mullinahack mills, whose own watercourses ran northwards to join the Liffey nearby. A revetment, in this context a lining of timber set along the sides of a water channel to prevent the banks from collapsing, may be represented by slight timber fragments projecting from beneath one of the culvert walls, possibly the oldest surviving element on site. The most recent phase of the channel appears as a red-brick culvert, a covered underground conduit, likely built considerably later than the medieval timbers beneath it. John Speed's 1610 map of Dublin City shows a watercourse running along St. Thomas Street, between St. Catherine's Church and John's Lane West, near an area marked as the mills, placing the Glib Water firmly within a documented landscape of milling and water management on the city's western edge.

The physical remains are not visible above ground; what survives does so in the archaeological record rather than in any accessible feature at street level. The interest here is more cartographic and contextual than visual. Speed's 1610 map, sections of which are held in various digital collections, rewards close attention: the watercourse and the mills appear together in a part of the city that is easy to walk through without any sense of the industrial and hydraulic complexity that once operated just outside the medieval walls. The junction of Oliver Bond Street and Augustine Street is ordinary-looking enough today, but it sits at what was once a functional corner of a living water system.