The tramway ran from Llyn Eigiau, where temporary lines ran north along the line of the dam (which was ¾ mile in length), down to Dolgarrog. The line was built to standard gauge, and largely utilized the route of the former Cedryn/Eigiau Quarry tramway which ran along the lower slopes of Moel Eilio, though at Pwll Du, about half a mile above Coedty reservoir, a small northerly diversion was made in order to avoid a former small incline.