Most people who think of the River Liffey picture it cutting through Dublin, but the river has a long life before it reaches the city, and at Harristown in County Kildare it passes beneath a bridge that has been doing its job quietly for the better part of four centuries. The structure spans roughly sixty metres across the westward-flowing Liffey, carrying a road just over five metres wide, and its seven arches give it a scale that feels slightly out of proportion with the rural surroundings.

Writing in 1991, historians O'Keeffe and Simmington described it as a tall, stately seven-arch bridge, a phrase that captures something real about its presence. It is built from random rubble masonry, meaning stones laid without regular courses, though in this case the work is described as being of excellent quality. The bridge features triangular cutwaters on both the upstream and downstream faces; these are the pointed projections that jut out from the piers to divide the current and reduce the force of the water against the structure. The parapets are low, at around three quarters of a metre, which gives the bridge a somewhat exposed, open feeling along its carriageway. O'Keeffe and Simmington placed its construction in the second half of the seventeenth century, a period when substantial bridge-building in Ireland was often tied to the needs of colonial administration, military movement, or the consolidation of landed estates following the upheavals of mid-century conflict.