The bridge is c800m from the main A499 at the hamlet of Pontllyfni, and carries a minor road over the Afon Llyfni (Llyfnwy). This is an early, precisely dated, single span country bridge.
The bridge was built in 1612 at the expense of Catherine Buckley at the cost of £20, in memory, it is said, of her fiance who was drowned crossing the river here. It was in need of repair, as presented to the quarter sessions in 1750, and was widened by 75 cm on the upstream side later, the widening seriously damaged by a flood in 1935 after which it was reduced to its original width.
Built of local stone rubble,the bridge consists of a single arch spanning 6.6m rising 2.3m above the water, formed with well-shaped voussoirs set back under a regulating course, and a low flush parapet coped with unshaped stones on end, rising in straight sections to an off-centre peak. The carriageway is 2.1m across, plus parapets of 40cm width. At the S end, on the downstream side, a badly lettered stone panel records the inscription CATRING BWKLE HA / TH GIVE 20 POVNDS / TO MACK THIS BRIDGE / 1612. (The same wording has been recreated on a much later slate plaque on the bridge).
At the N end, the causeway approach has 2 small square flood culverts.