Berlin Wall

The Berlin Wall was a barrier constructed by the German Democratic Republic (GDR,East Germany)starting on  August 13, 1961, that completely cut off West Berlin  from surrounding East Germany and from East Berlin.
It was claimed that  the wall was erected to protect its population from fascist elements conspiring to prevent the "will of the people" in building a Socialist State  in East Germany.
Before the Wall's erection, 3.5 million East Germans circumvented emigration restrictions and defected from the GDR, many by crossing over the border from East Berlin into West Berlin, from where they could then travel to West Germany and other Western European countries.
Between 1961 and 1989, the wall prevented almost all such emigration.
In 1989,after several weeks of civil unrest, the East German government announced on  November9, 1989 that all GDR citizens could visit West Germany and West Berlin.
Crowds of East Germans crossed and climbed onto the wall, joined by West Germans on the other side in a celebratory atmosphere. Over the next few weeks, a euphoric public and souvenir hunters chipped away parts of the wall; the governments later used industrial equipment to remove most of the rest.

The fall of the Berlin Wall paved the way for German Unification which was formally concluded on October 3,1990.