"After that, they travelled in peace as far as Y Traeth Mawr"
View across the Traeth Mawr as it is today
Creative Commons Attribution Share AlikeView across the Traeth Mawr as it is today - Credit: Ken Bagnall

Y Traeth Mawr (‘the great stretch of sand’) was the name given to an area of sand and salt marshland separating the old Merionethshire from the old Caernarvonshire (or, in Mabinogi terms, the commotes of Ardudwy and Eifionydd). Situated at the estuary of the River Glaslyn, it was regularly flooded by the sea and was notoriously dangerous to cross. Between 1808 and 1812, at the instigation of William Alexander Madocks, an embankment, known locally as ‘the Cob’, was built to exclude the sea from a large portion of the Traeth Mawr. Today the Cob carries the A497 from Porthmadog to Minffordd, a cycle path and the Ffestiniog railway