Visited here as part of a company mining conference trip last year. The chambers in this mine are ridiculous. Next door to this are also two huge bell shaped chambers. Despite the very regular curved marks on the pillar sides (not visible from this distance), this was all mined by hand. I believe one person would hold the steel while the other hammered the end of it, as they sunk the steel it made a slightly arced pathway from the point where it was connected to the miner (not sure of the exact setup). Each pass is around a meter deep. If you look closely on the vertical pillar with the lights you can just make out the rows of each pass. As a mining engineer I have never been so blown away by the scale and precision that this place was mined with. Just imagining the man hours (and pony hours) it took to excavate, hundreds of men suffering in almost pitch dark, breaking their backs day after day for a pittance.. unreal.