Ps I also worked in a phone exchange building. Cool thing was that there were half floors. 1, 1 1/2, 2, 2 1/2 etc. These floors were in fact half height like in the movie Being John Malkovich. Except there were no offices, they were used to route the huge cable trunks between floors and rooms.
These days with single fibers replacing thousands of cable pairs I'm sure they're a lot more roomy than they were back then.