The main crossing, built in 1856, carries four wide, low segmental arches of coursed limestone across the river, with a string course running above the arches and a parapet of large limestone blocks. Its south arch fans outward on the western side to meet the angle of the approaching road, a small but telling piece of practical geometry. What makes the site stranger is that the 1856 bridge was itself a replacement, and the thing it replaced has not entirely gone away.

The 1712 bridge, which the Victorian structure superseded, partly survives at the northern end, now spanning ground that floods only occasionally. Four of its original fifteen arches remain, built of random roughly-shaped stonework with cut-stone voussoirs, the wedge-shaped blocks that lock an arch together, and bluntly pointed cutwaters designed to divide the current and reduce pressure on the piers. A later iron railing runs between chamfered stone piers along the parapet. But the 1712 bridge was itself not the first. Embedded in a pier beneath the north arch is a stone inscribed with the cryptic Latin fragment 'M: OS: D: OS: A: M / POS', one of nine inscribed stones recorded here in 1810, one of which bore the date 1631. The lettering style on the surviving stone suggests a sixteenth or early seventeenth-century origin, and local tradition holds that the stones were brought from a monastery in Ballydaheen. A bridge at Mallow was swept away by flood in 1628, and by 1650 a structure here was described as too delicate to bear the weight of two siege guns. A bridge appears on the Down Survey barony map of 1655 to 1656, so the crossings had been coming and going for a long time before anyone laid the present limestone. An inscribed stone from the 1856 build, found around 500 metres to the north-west, now sits in the wall of a shopping centre near where it was discovered, which is perhaps the most contemporary chapter in a long story of displaced masonry.

The fragment of the 1712 bridge is visible at the northern end of the present crossing, and the inscribed stone in the pier beneath the north arch rewards a closer look if the water level allows. The site sits roughly 200 metres south-west of Mallow Castle, and the smaller bridge immediately north of the main crossing, a mid-nineteenth-century structure of two segmental arches over a tributary of the Blackwater, is easy to overlook but completes the sequence.