Mina Victoria.
A nice, low key museum and underground mine visit that we found last year in Spanish Pyrenees, just over the border from France in Val D'Aran. Drive up most of the way then walk. Also a round trip via mountain tracks if you have a 4x4 to Mina Margarita. Summertime only!
Les
Picture 1:Mina Victoria has gated adits (with very widely spaced bars........)
Picture 2:Mina Margarita is open and unattended.