Last weekend I was in Berlin and a great coincidence happened. On Friday afternoon I took the tube from a relatively central station to one of the main ones (Alexanderplatz). I sat right in front of a girl of my age and left the tube without talking to her or anything. She stayed in the tube. Then, after dinner, at around midnight, I went to Alexanderplatz station again... and I almost crashed into her! We both realised this, smiled, said hi and went to our respective (different) platforms.