Not documented on here and i was passing through so thought i would post it up.
History (Forgotten Relics)
Overshadowed by its bigger and more celebrated brother called Rhondda, the 164-yard Gelli Tunnel formed part of a line built to connect the collieries of the Rhondda valley with the Swansea Bay ports. As it transpired, the considerable efforts of its engineers never reaped great financial dividends due to the tortuous gradients involved.
Heading eastwards from Cymmer, trains clung to the northern side of the Afan gorge, disappearing into Gelli Tunnel on a curve. The first one did so on 2nd July 1890.
Both portals and the original lining were built in masonry. An additional two-course brick lining was inserted towards the northern end as part of a subsequent strengthening scheme. A handful of refuges were also provided.
The tunnel became surplus to requirements on 13th June 1960 when British Rail opened a connection to the Great Western's parallel Abergwnfi route from the Gelli ground frame.
Although the structure remains generally in decent order, the eastern portal has deteriorated considerably since closure.
Thanks for looking