Haven’t seen any real in many years but your guess is correct!
It’s 1-person pillboxes and every one I seen is probably dated to 1910-1930-ish. Or even older…
Common as external observation positions with a small bunker/pillboxes around larger military bunkers, defense facilities and old defensible objects such as factories. Probably 20-25 years since I ran on one.
Idea of elevator is a close guess too, because everyone I seen the inside of has a hatch with a ladder down, then a little tunnel toa small bunker with some pillboxes around, all in concret engulfed in mountains and cliffs. And that was also the place for the rest of the guard force to stay waiting on thiers guard pass in the lookout pillbox.