People in 1920s Berlin nightclubs flirted via pneumatic tubes (2017)
Berlin had one of the largest pneumatic mail systems in the world. A (highly recommended) Berlin Unterwelten tour covers it. There is still a big, beautiful Rohrpost building in Mitte close to the big Synagogue.The Real store at Leopoldplatz has a pneumatic tube system that reaches every cash register. You can see the tubes go up and along the ceiling. I believe that it's one of the failed Walmart stores from their disastrous attempts to conquer the German market.