The one at Derreenacullig, crossing the Loo River in County Kerry, earns its attention more quietly, through the particular care taken in its construction at a point where a modest rural crossing could easily have been built without much ceremony at all.

The bridge is around 7.5 metres wide, with its long axis running northeast to southwest, and its centrepiece is a single segmental arch spanning roughly 10 metres. A segmental arch is shallower than a full semicircle, which gives it a flatter, more graceful profile, though it demands precise stonework to hold the load. Here the voussoirs, the wedge-shaped stones that form the arch itself, are cut and dressed rather than rough-set, indicating a deliberate investment in craft. The body of the bridge is built in random ashlar, meaning the stones are shaped and laid without strict courses, giving a solid but less formal appearance than fully coursed masonry. On each face of the arch, a pair of full-height pillar-buttresses flanks the opening, reinforcing the structure against the lateral pressure of the river. A string course, a narrow projecting band of stone, runs along the base of the parapets, and the parapets themselves are finished with vertical stone coping. At the northeast end, the parapet walls splay outwards to meet a wider approach road, a detail that speaks to practical thinking about how vehicles and animals would actually use the crossing. Just beyond the bridge on the northeast side, on the flood plain, there is a lintelled overflow arch, a secondary opening designed to carry excess water during high flows and to relieve pressure on the main structure when the Loo runs hard.