Part of the Maenofferen Slate Mine (NPRN 400427), these rock cut tunnels were excavated prior to 1902 according to plans held by J. W. Greaves and Sons Ltd. The tunnels provide a connection between the Main Incline (also known as the Back Vein Incline), the Mill Floor Incline and the Dressing Mills. Within the tunnel branch between the Main Incline and the Dressing Mills is a passing loop. A branch of the Mill Floor Tunnel originally exited to the N of the current exit, although this is now blocked by a Breeze Block wall and no tramway rails were recorded within this branch. The tramway rails survive within the remainder of the tunnels, although they have been removed outside the Dressing Mills end next to the weighbridge (NPRN 415910)

References: Plans referred to are held by J. W. Greaves and Sons Ltd, Blaenau Ffestiniog

Spencer Gavin Smith, RCAHMW, August 2011