What is "bwlch-y-ddeufaen"

Bwlch-y-Ddeufaen ( Welsh: Gap/Pass of the Two Stones) is a mountain pass in Conwy county borough, north Wales, traversable only on foot or horseback, following the former Roman road from Caerhun (Canovium) to Caernarfon (Segontium). The route may be followed by road to Rowen or to Llanbedr-y-Cennin and from either, the way, through a mountain gate, is a clearly marked green path to Abergwyngregyn. The route lies between the peaks of Tal y Fan and Drum, in the Carneddau range in north Snowdonia. The distance from Rowen to Abergwyngregyn is about nine miles of mostly high mountain footpath. Near the Abergwyngregyn end, the route forms part of the North Wales Path.