I first went to Berlin in 1983 (when it was still a city divided between East and West and controlled by USSR, USA, UK and France). The friends who lived there have special passports (different from German ones) and avoided German National Service.
My recent visit to Berlin reminded that the Berlin Wall ran through the Platz and in fact it is marked on the roads and pavements today.
There are a few sections of the wall standing in their approximate location.
My recollection from 1983 is that you would climb a scaffolding and wooden stairwell and look over the wall – to the East. (I have scanned this in, so apologies for quality).
There is more on the history of Potsdamer Platz at Wikipedia – for those interested in a more depth explanation of the location and its significance.
Of course, the Grand Hyatt, Berlin is located nearby:
I still have my East German transit visa, which was required when I travelled from London via Holland, to Berlin. The trains used to run through East German stations – although they clearly never stopped. My old passport also has two DDR stamps in it.
Berlin is a fascinating city – it’s history, division and current position makes it one of my favourite cities in the world. Well worth a visit, good value and plenty to do.