What is visible above ground, the five-arched limestone crossing known as Lissenhall or Balheary Bridge, is already old enough to command attention. What lies beneath is older still, and the two together tell a story about how roads and rivers have been negotiated at this point for the better part of six centuries.

The bridge has been dated to the period 1450 to 1550, based on the work of O'Keeffe and Simington, and it appears on the Down Survey map of 1655 to 1656, the ambitious mid-seventeenth-century mapping project that recorded landholdings across Ireland following the Cromwellian settlement. Built of mortared limestone masonry, it is constructed in three abutting sections, and the middle section retains slightly pointed arches that carry wattle marks, the impressions left by the wooden framework used to support the arch during construction. The upriver cutwaters, the projecting piers that divide the current and protect the structure from debris, are triangular with semi-pyramidal cappings. When ground penetrating radar and test excavation were carried out in advance of the proposed Metro North project (Licence no. 09E0464), the results were striking: much of the medieval fabric had survived intact within the existing bridge structure. Investigators also found a wall running along the eastern side between Lissenhall and Balheary Bridges, and beneath the road on the western side, an arch or culvert predating the one currently visible. This earlier feature suggests the road itself went through a significant earlier phase, possibly preceding the widening or redevelopment that took place in the late seventeenth or early eighteenth century, according to Channing's 2009 analysis.

The bridge sits within Balheary Demesne, off the main road just north of Swords, and is not a site set up for visitors in any formal sense. There are no signs directing attention to it, which is part of what makes it worth seeking out. The wattle marks on the pointed arches are best observed when the light is low and raking, which tends to mean early morning or evening visits in the clearer months. The river setting and the age of the stonework reward a slow look rather than a quick one.