Well if those are guarded by evil people or satanists it may definitely be, it happens in Italy as well, (now quite) some time ago, there was specially a valley with weird mountains where people would walk and adventure by, many went missing, a tv troupe of a late night show (showing conspiracies, catching ghosts, all those kind of stuffs) went there to dig, short story they found out the rude way that the mountain is a secret military base where presumably there were alien interactions

I think we know the usual plot, probably that was an entrance to one of their bases / bunkers and people ended up being abused / killed(or sacrificed)