5. There are Pneumatic Tubes in the Library
Until a few years ago, the New York Public Library still used pneumatic tubes to fulfill book requests. To request a book from the stacks, you would fill out a call slip that would be sent through the tube to one of the eight levels of stacks where an employee would find your book then send it via conveyor belt to the same spot where you submitted the slip.
The system was so efficient that it mainly went out of use because the canisters were too difficult to replace. Officially retired only a few years ago, the pneumatic tube system was receiving upgrades and new installations until 1998 according to Atlas Obscura. You can still see the tubes in the library today in the Rose Reading Room.