The Berlin Wall was built in 1961 to stop an exodus from the eastern, communist part of divided Germany to the more prosperous west.
Between 1949 and 1961 more than 2.6 million East Germans, out of a total population of 17 million, had escaped. Many were skilled professionals and their loss was increasingly felt in the German Democratic Republic, or GDR, as it was called.
With the country on the edge of economic and social collapse, the East German government therefore made the decision to close the entire border, and erected the wall overnight, on 13 August 1961.
It was often referred to by eastern authorities as the anti-fascist protection barrier, to protect East Germans from the west.How was it built?
The concrete barrier, complete with 300 guard towers at regular intervals, was 96 miles in length and 13 feet high, though to start with it comprised temporary barriers of barbed wire coils.
The erection date of 13 August 1961 was deliberately chosen because it was a Sunday during the summer holidays. Over days and weeks the barbed wire was replaced with vertical concrete slabs reinforced with iron bars, and hollow blocks.
Photograph: East German soldiers set up barbed wire barricades in Berlin on 13 August 1961. Photograph: AP
Nothing was allowed to stand in the way of the wall. Houses on streets, such as Bernauer Strasse, where the pavements were in the west, and the backs of the houses were in the east, became part of the border construction.
The authorities simply ordered the bricking up of front entrances and windows. There are documented cases of people jumping from windows to avoid being locked into the east in their own homes.