Bundesdorf Bonn
For most people, the city of Bonn is known as the capital of West Germany. And rightfully so, because, well, it used to be the capital of West Germany (and the seat of government of united Germany between 1990 and 1999, as the reunification made Berlin the nominal capital). I mean, the city was officially called a federal capital for the first time in 1970, but you get the idea. It was always meant to be temporary etc., because Berlin was not avaiable at the time.
But it didn't have to be this way. The other, strong candidate for the seat of government/capital of West Germany was Frankfurt am Main. Politically speaking, it could make sense, as Frankfurt was the location of the Frankfurter Nationalversammlung, the the first freely elected parliament for all of Germany that was created during the revolution of 1848. So, technically speaking, it was the perfect place for the capital of the new, fully republican, Germany, where everything is finally Bundes (federal) instead of Reichs (imperial), as if it makes any difference.
Frankfurt wanted really hard to be a capital. The city already started the construction of the plenary hall (which is now the broadcasting hall of the Hessischer Rundfunk company) and the mayor of Frankfurt has already had a speech of thanks recorded on Radio Frankfurt. The capital in Frankfurt was, after all, prefered not only by the SPD, but also by the Hessian branch of CDU. However, Adenauer made a report in which it was stated that the vote for the capital in Frankfurt would lead to a humiliating defeat of the party, which encouraged the Hessian CDU to vote for Bonn and indeed the Parliamentary Council voted 33/62 for Bonn. The first Bundestag also debated and voted on the issue, but Frankfurt lost again.
The capital in Frankfurt would be cheaper, better both politically and after the reunification, it would probably stay the capital. But Bonn was so preferred by Adenauer, as it would be surely just a provincial capital and not something permanent, as the permanent capital of reunited Germany should be Berlin, period. Weeell, not gonna lie, the fact that he used to be a mayor of Cologne and that he had its home between Köln and Bonn was probably quite important as well. I mean, today you can use the same Stadtbahn line if you want to visit both his home and Bonn from Colognem after all.
But hey, there was a chance that Bonn would stay the seat of government after the reunification. Although it was decided that Berlin will be the capital of reunited Germany, you can always have the capital and the seat of government separately, like in the Netherlands. But it was decided by the narrow vote that Bundestag (and most of the offices) will move to Berlin. There was a proposition that the Bundesrat and the president should move to Berlin, with the Bundestag and the cabinet staying in Bonn. Like, y'know, many other institution of the Bundesrepublik that are deconcentrated and in many different locations in the country (including the most important courts etc.), as opposed to some centralizing deepshits like Poland.
The vote in the Bundestag showed that the regional origin of the MPs was of great importance. MPs from North and East Germany mostly voted for Berlin, those from South and West Germany mostly for Bonn. In addition, there is a strong correlation between denomination and voting behavior. In contrast, 67% of the Catholic MPs voted for Bonn, but only 36% of the Protestant MPs. But still, blame the Ossis, I guess.
Some offices still stay in Bonn, as well as some ministries (the federal ministry can be either in Berlin or in Bonn, but has to keep the secondary office in the other city), the second seat of the Chancellor and Bundesrat, among others.
There is also one asterisk – the Bundesrat actually decided in 1991 to stay in Bonn, but after 5 years it also decided to move to Berlin.