The bridge that crosses the River Liffey at Coneyburrow looks, at first glance, like a fairly ordinary rural crossing. It is not. What appears to be a stone structure is in fact a concrete replica, faced with stone to give the impression of antiquity, and beneath its central arch the remains of a genuinely medieval bridge still sit on the riverbed, submerged and largely unnoticed by those passing over it.

The original crossing was reputedly built in 1308 by John le Decer, then Mayor of Dublin, making it one of the earlier documented bridges on the Liffey. By the early twentieth century, the structure was still standing and detailed enough to be described with some care: four arches, the two outer ones rounded, the two inner ones pointed, with a roadway of roughly 2.8 metres in width. Most striking were the wattle imprints visible on the undersides of the arches, traces left by the organic formwork used during construction, where flexible rods woven together supported the wet mortar until it set. That original bridge was eventually replaced, some time before 1939 when the Ordnance Survey map of that edition already names the current structure as New Bridge. The replacement was built to a three-arched design with cutwaters, the angled projections that deflect the current away from the piers, and refuges, small recesses where a pedestrian could step aside to let a cart pass. An underwater archaeological survey carried out in 1995 found a pier and stone paving from the 1308 structure still lying beneath the central arch of the present bridge. There had also been an ancient ford somewhat downstream of the bridge, predating even le Decer's construction, suggesting this was a crossing point of some importance long before the medieval period.