It once was a very complicated business and a risky journey to cross the Glienicke Bridge. Lengthy negotiations were required, and military and intelligence services had to be involved. Not to mention the diplomats. 

During the Cold War the Americans and Soviets used Glienicke Bridge for the exchange of captured spies as it was a restricted border crossing between the Eastern Bloc and the American sector of West Berlin. Thus, it became known as the Bridge of Spies. The famous exchange of the Soviet spy Rudolf Abel for the American pilot Gary Powers took place here in 1962, a story vividly described by Stephen Spielberg in his movie “The Bridge of Spies”. That was the first and probably the most well-known case, but definitely not the only one. In 1985 23 American agents who had spied for the West were exchanged here for one Polish and three Soviets who had spied for the East. The final exchange took place in 1986 when the Soviet dissident Anatoly Shcharansky (a.k.a. Natan Sharansky) and three Western agents were exchanged for Karl Koecher and four other Eastern agents.

The Glienicke bridge as a venue for prisoner exchange has appeared frequently in fiction, including John Le Carré's novel Smiley's People and the related BBC miniseries, as well as in the 1966 Harry Palmer film, Funeral in Berlin, based on the novel of the same name by Len Deighton.

Read more https://en.m.wikipedia.org/wiki/Glienicke_Bridge