Ahh this brought back fond memories Richard, thanks for sharing.
I went there as a teenager. Once down, one of us borrowed a lamp and we set off in search of adventure. Off we went into a tunnel and into smaller and smaller caves. For about 15 min we travelled, the tunnel getting narrower and more cramped as we went. As a joke, the lamp holder switched off the lamp and never have I experienced such complete darkness and almost total silence. Being a wuss, I begged for the light to be switched back on, and eventually we turned back (it gets a wee bit eerie down there after a while).
On the way back we took a wrong turning (descending rather than ascending) and went into a maze of tunnels that none of us recognised, and didn't seem to go anywhere. By now we were all totally panic-stricken, lost in what seemed to be the bowels of the Earth. Somehow retracing our steps (well, not exactly steps, what are they called when you are on your knees

) we found the path that went upwards, but everything looked so different the other way round, we were still confused for a good while after that.
Anyway, we lived to tell the tale, and it was the most amazing experience. I would thoroughly recommend a visit there