As a child I spent several summers riding along with my parents when they drove OTR, some with my mom others with my dad. I remember the two times we delivered to underground warehouses. I thought it was the coolest thing. It was a little unnerving at first because there's so little room to maneuver, but skilled drivers manage it. This guy either has to little or to much imagination. There's nothing suspicious about them just the marvel of innovation.

Once upon a time (in the mid 90s) I worked as a service tech for electronic equipment. One of the customer sites I went to was in a place like that south of St. Louis. It was originally some sort of quarry/mine. I had to drive about half a mile into the side of a hill. I was kind of freaked out. The customer was a music duplication service, made 1000s of copies of cassette tapes from studio master tapes. They said it was a great place, since they had no outside radio or magnetic interference to worry about, and got pure copies.