The 68 tram in Berlin has stretches that are fully in the forest that were designed to allow people to go to nature for recreational reasons.

It’s gorgeous, in some parts it feels like you’re in a Miyazaki movie

Awesome, this why EU Public Transportation is light years ahead of The USA.

The only thing I would make me change my mind & be totally against it is if the route required destroying the forest/not already established & unused roadway(s).

In early-20th-century America, they called these interurbans. You could get (slowly) from New York to the Midwest using only a chain of them.

Check out Stubaitalbahn too if this makes your caverns fill.