S-bahn entrance must be somewhere close...
Day or night, pedestrian traffic is heavy around the Zoo Bahnhof. Station for the Interzone trains carrying civilian traffic between West Berlin and West Germany, transfer point between U-bahn, S-bahn, and buses for commuters, and meeting point for anyone not sure where else to meet -- that was the place that GI's ironically knew as "Zoo Station."
The dominant theme here was the S-bahn, operated as the urban commuter railway unit of the Deutsche Reichsbahn. Elderly rolling stock of the S-bahn rumbled overhead on clockwork patterns throughout much of the day, and even all night on weekends. It all was bewildering to the newcomer, whether GI or immigrant "guest worker" trying to thread their way through the bustle and the hustlers.
For the GI, politics made the scene more complicated. The East-controlled
S-bahn system was off-limits, but the station had a handy and massive Men's
room. And what about the train platforms for the Interzone service?
When my sister and classmates came on a quick tour in 1969, I shuffled
in with the crowd, bought a platform ticket and climbed the stairs to say
goodbyes, but compromised by taking no pictures. They were off on
the night train to Munich. I remained. Steam locomotives breathed
heavily at the end of long green trains -- almost as heavily as I breathed,
wondering if I might be breaking some Army regulation that no had thought
to mention to me. It was the 1969 edition of "don't ask, don't tell."
 Continue on the tour. Weitermachen!