I went past this mausoleum a year or two back whilst on a touring holiday, it wasn't a stop off, and was told that it was dug out of the mountain by forced labour that were underfed and quite a few hundreds died in the process in a similar fashion to the way other national socialist movements at the time disposed of their opponents.
Apparently hardly anyone was going there so Spanish authorities closed the gates on this lot mainly because so many Spaniards can't face the sadness and cruelty of it's history, so I was told.
Regards, ippy.