Interesting piece on Cambrian (Glyn Ceriog) tonight on BBC's One Show - diving to the lower chambers. They didn't say where it was but the divers posing next to the huge riveted air receiver gave the game away to us in the know...
Brilliant bit of video footage - some really interesting artefacts down there:- Steam winder, wagons, rails but perhaps the most poignant, the former miners' signatures on the slate walls written with the sooty flames of their carbide cap lamps.
It may be available on i-Player, worth a look.
Clive