Concealed within the fabric of the existing structure, sandwiched between its 19th- and 20th-century components, is an earlier bridge that was never demolished so much as absorbed. Most drivers crossing it have no reason to suspect they are passing over something far older than the road they are travelling.

The archaeological record for this crossing reaches back at least to the 17th century. The Down Survey, a remarkable mid-1600s mapping project that recorded landholdings across Ireland following the Cromwellian conquest, depicts a tower house castle at Ballinacurra standing directly beside a bridge over the Ballynaclogh River. A tower house is a compact, vertically arranged fortified dwelling, common across medieval Ireland, and the one shown here appears on two separate Down Survey maps: the map of South Liberties Barony and the map of the parishes of St. Michael's and St. Nicholas, the latter of which also shows a watermill nearby. The combination of castle, mill, and river crossing in one small area suggests this was a place of some local economic and strategic importance. When archaeologist Rex Bangerter carried out a riverine assessment of a 300-metre stretch of the Ballynaclogh River as part of planning for the Limerick southern ring road, two significant features came to light: the encased early bridge structure within the existing crossing, and a series of timber pilings found 75 metres downstream, possibly the remnants of an even earlier crossing or river-related structure.

The bridge sits within a stretch of river that was assessed ahead of road construction, so access to the riverbanks in this area may be limited depending on the state of ongoing development. The pilings downstream are not visible above the waterline under normal conditions, and the early bridge structure is entirely hidden within the modern stonework, so there is little to see in a conventional sense. What rewards a visit here is more a matter of orientation: standing on a working road bridge and knowing that you are, in a small way, inside a piece of medieval infrastructure rather than simply on top of it.