The Berlin Wall was a barrier constructed by the German Democratic Republic (GDR, East Germany) starting on 13 August 1961, that completely cut off 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 surrounding East Germany

Germany

Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 and from 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...

. The barrier included guard towers placed along large concrete walls, which circumscribed a wide area (later known as the "death strip") that contained anti-vehicle trenches, "fakir beds

Bed of nails

A bed of nails is an oblong piece of wood the size of a bed with nails pointing upwards out of it. It appears to the spectator that anyone lying on this "bed" would be injured by the nails, but this is not so...

" and other defenses.