The path from the harbor towards Penrhyn Castle and on to Bethesda is a former railway bed, originally built specifically for the transport of slate from the local quarries. This stone bridge, known as Cegin Viaduct, commemorates that railway history.
As the oldest known multi-arch railway bridge in Wales (built between 1798 and 1800), the viaduct is internationally important as a historic industrial monument and is listed (Grade II).
The bridge has three arches, approximately 26 meters long between each abutment, 5 meters wide, and 3.2 meters high. Each arch has a span of 5 to 6 meters and a height of approximately 1.8 meters.
The viaduct was thoroughly restored in 2015. Sources:
ygc.cymru/project/cegin-viaduct-restoration-porth-penrhyn-bangor
coflein.gov.uk/en/site/401047/