The Berlin wall assumed its final appearance at the end of the 1970s, when the outer wall to the west was replaced by mass-produced sections of reinforced concrete. Strict security was maintained at all times, of course, with the construction teams having to work under close watch behind wire fences. Each segment of the wall was 11' 9 3/4" (3.6 m) high, 3' 11" (1.2 m) wide, 6" (15 cm) thick, and weighed over 2 1/2 tons. The segments had originally been developed in the early 1960s in order to build grain and fodder silos for East German farms. The white surface facing west quickly became a provocation for all genuine and would-be artists, who began to "beautify" the wall under the cover of night. Whether abstract or realistic pictures, graffiti or commentary, the Berlin wall had it all. It was strictly forbidden to approach the wall directly, much less touch it. The wall stood on East German territory and was therefore officially off-limits. The commentary was not infrequently full of bitter satire and wit, a reaction to the seemingly hopeless situation of life with the wall. For example, one person writing in English proclaimed "Look at the bright side of life." But the writing was laterally inverted, so it would have been pro perly legible only if the wall had become transparent - to someone seeing it from the eastern side.

The frontier and its fortifications ultimately became so sophisticated that almost the only way to get from one side to the other was to do it legally. The Glienicke Bridge, aptly christened the "Bridge of Unity" by the East German authorities, linked Berlin with Potsdam and became the famous location for the exchange of agents, political prisoners, and dissidents. In 1962, for instance, it was here that the American pilot Gary Powers was exchanged after the U2 incident, in which he had been shot down over the Soviet Union. One of the last people to reach freedom via the Glienicke Bridge was the Soviet Jewish civil rights activist Anatoly Scharansky.