To reach the border in the South-East of Berlin, you would have to get onto the 'Avus' and the 'Berliner Ring', which is a freeway system going around the city. At that first border crossing, where you exit West-Berlin into East-Germany, called 'Dreilinden', you could already expect long delays due to the long lines of travelers.
All cars had to line up at toll-booth type of controls, and had to show their travel documents at the first booth. The documents were taken from you and transferred on a covered conveyor belt to the second booth. A transit visa was issued right there (for a fee?) and valid for that day only. Your car crawled from booth 1 to booth 2 where you would receive your documents and the visa.
Now if your travel documents were out of the ordinary, the East-German official would ask you to pull aside for a secondary inspection. And this would usually be the case for us, as my husband still held his Iranian passport. If you were lucky, there would be only a few additional questions and a short delay and you were given your visa. If you had an official who was more of a bully, he could take the car apart. And they really would. They asked people, or let's say told them to get out, remove everything from the car and trunk. Sometimes they would take out the rear seats and check every nook and cranny (happened to my parents during a spot check).
And yes, once they went that far, that my husband had to follow a guard into a separate shack and undress completely in front of them.
So, with our visa in hand, seats mounted back in (actually this had not happened to us) and pants zipped up again, we were on our way through East Germany via 'Madgeburg' towards 'Marienborn/Helmstedt', the next border into the Federal Republic of Germany.
On the 2-lane freeway, speed limits were kept at 100km which you did not dare to break as highway patrol was hiding behind every bridge and pillar. You were not allowed to leave the freeway, except at service areas or rest stops. We would often stop at 'Ziesar', the middle mark for us, for a bathroom break in a 'Mitropa' restaurant or we would shop for a snack at the 'Intershop', only Deutsch Mark accepted.
It was not allowed to communicate with East-Germans at these rest stops. The Stasi was watching everywhere. Families who were torn apart due to the wall would sometimes meet at a rest stop and speak at distance without touching. We have witnessed that a few times. You were not allowed to exchange anything with an East-German citizen, so some people would leave western newspapers and magazines in the trash for others to retrieve. And you would have to drive this route in a certain acceptable time-frame. If there was an accident or other delay, you would be questioned about it at the exit crossing. Usually, they already knew about it, if police had been involved.
We always exhaled a breath of relief when we crossed into the West after going through the last border control where they would retrieve the visa from your travel document.
It was such an ordeal every time and the thought that we would have to return the same way would dampen our family visit.
Below are a few links that show photos of these border crossings. Looking at them, they bring back dark memories.