From pictures i've found Im thinking its this cravass / adit that been filled in with general rubbish and then collapsed. In more recent years the European Union has spent lots of money on filter pools to try and clean the water outlet of the mine so maybe the water in this old picture had been...

Theres a wealth of knowledge here! Look up Rosevale Mine they seem a good bunch wish i was closer so i could beg them for a look! Minimum I would say helmet wellies and decent torches, I've used "LED Lenser" for maybe 10 years now working nightshifts and recreational abandoned mines.

Hello new here but i was on adit now for many years as "Mr Sam" although didn't post a great deal. Has anyone on here got any more info on a recent surface collapse at Frongoch? I happened to see some pictures posted on a 4x4 group as the mine surface is now used as a Range Rover breakers yard...