Caving - Poachers. Will keep you occupied for an hour or two.
Mine-wise - lot's more options. Bwlch-y-plwm, Cae Coch Sulphur Mine, Cwmorthin or Rhosydd being initial suggestions. Also, you could get in touch with Parys Underground Group or Great Orme Exploration Society.
If you want to go to Clwyd, or whatever it is these days, Denbigh, or Flint, or Wrexham, or Maelor, then contact UCET.
Robin