 North of Llangefni, the railway follows the course of the River Cefni in The Dingle (Nant Y Pandy).Having followed the river through the narrow valley, over bridges and through cuttings, the railway crosses Llyn Cefni, the island's second largest reservoir.The railway continues north-west over easier terrain towards Llangwyllog and Llanerchymedd, where it turns north, running to the west of Llyn Alaw toward Rhosgoch.