Yeah, I was there.
I came out of evening class at 10 and drove with 2 friends in my car from Wedding to Kreuzberg.
We passed Checkpoint Charly at Friedrich Strasse and noticed a huge raving crowd.
normaly its a well lit kinda dead end street with patroling guards, but this wasn't normal.
wtf is going on? It was kinda frightening first 'cause we didn't know if something bad had happend so I turned the casette off & switched to radio.
and there it was - on every station - the east german people may travel without visas.
now we were getting very excited, my mates decided to watch it on tv, so I dropped them off and I went home and watched it on telly for about 10 minutes.
then I grabbed my bike and went to Prinzen Strasse which was about 2 min by foot.
I went about 10 meters into enemy territory - lol and everyone was cheering and shaking hands, offering beers and banging on the cars with their hands. (sounded like cardboard boxes, hehe).
Then I decided to have a look and whats going on at Oberbaum bridge.
same thing there, except you had a bridge to cross and that was kinda scary.
I went over there for the first time but went back after about 1/2 an hour or so.
I still didn't trust the guards and I didn't want to get stuck in east Berlin, so I stayed on the safe west side and talked & greeted the east german folks pouring in.
I had tons of beer that night gave away quite a few.
won't forget that night, I tell ya.
here's an old map with the border (pink/red) on it.