The Transit Agreement of 26 May 1972 arranged access to and from West Berlin

West Berlin

West Berlin was a political exclave that existed between 1949 and 1990. It comprised the western regions of Berlin, which were bordered by East Berlin and parts of East Germany. West Berlin consisted of the American, British, and French occupation sectors, which had been established in 1945...

 from West Germany

West Germany

West Germany is the common English, but not official, name for the Federal Republic of Germany or FRG in the period between its creation in May 1949 to German reunification on 3 October 1990....

 (the Federal Republic of Germany (FRG)) and secured the right of West Berliners to visit East Berlin

East Berlin

East Berlin was the name given to the eastern part of Berlin between 1949 and 1990. It consisted of the Soviet sector of Berlin that was established in 1945. The American, British and French sectors became West Berlin, a part strongly associated with West Germany but a free city...

 and East Germany (the German Democratic Republic (GDR)) also secured the rights of GDR citizens to visit the FRG, but only in cases of family emergency.