Known historically as Castle Bridge, this modest structure served as the primary approach to Dublin Castle from Castle Street, funnelling visitors, officials, and goods across what was, for centuries, a genuine defensive moat rather than a civic amenity.

The bridge's strategic importance becomes clearer when you consider what surrounded it. Excavations carried out between 1985 and 1986 revealed the outer portion of the castle moat directly opposite the outer main entrance, and the geometry of the dig told an interesting story: the outer edge of the moat curved inward at this point to meet one end of a large rectangular barbican, a fortified gatehouse structure designed to control access and expose any attacker to fire from multiple angles, positioned in direct alignment with the entrance beyond. The find was documented by Lynch and Manning in 1987, and the site had also been recorded on the FMD map of 1978. Bradley and King, writing the same year, placed the bridge clearly in the historical record as the formal link between Castle Street and the castle itself. The picture that emerges is of a carefully engineered approach, where the bridge, the moat, and the barbican worked together as an integrated defensive system rather than as separate features.

Today there is nothing visibly bridge-like to observe from street level; the moat was long since filled in, and Castle Street presents itself as an unremarkable urban thoroughfare. What rewards a visit here is less about what you can see and more about the act of reading the landscape with the excavation findings in mind. Standing near the upper yard entrance to Dublin Castle, it is worth pausing to consider that the ground underfoot was, not so many centuries ago, a wet defensive ditch, and that the approach you are making on foot was once mediated by a gatehouse designed to make that same approach considerably more difficult.