The Berlin Wall was built in 1961 after the flood of people leaving Communist East Germany threatened to become an economic problem as well as a public relations disaster for the government.
Most of those leaving were the younger, more educated part of the population who voted with their feet against the repression and deprivation of the young East German state.
Estimates suggest that almost two million people left before the wall was erected in 1961. On the night between August 12th and 13th of that year, thousands of East German troops, police and labourers started work on the 165 km barrier, initially just with barbed wire. This was later replaced with the concrete wall which was accompanied by a strip of bare, mined ground.
Border guards working in watchtowers were given shoot-to-kill orders and were personally held to account if someone escaped.
More than 250 people were killed trying to escape in Berlin alone while hundreds more were killed along the border outside the city. One of the most famous deaths was that of an 18-year-old builder's apprentice.
Peter Fechter tried to climb the wall in 1962 but was shot during his attempt. He fell onto the East side and lay there for nearly an hour, bleeding to death from multiple bullet wounds in full view of West Berliners on the other side. A memorial is being erected at that spot this week to commemorate his death.