Berlin Wall Built (1961): Just past midnight during the night of August 12-13, 1961, East German soldiers and construction workers headed to the border of West and East Berlin. While most Berliners were sleeping, the workers quickly constructed a barrier made of concrete posts and barbed wire along the border.
When Berliners did finally wake, they found themselves stuck on whichever side of the border they had fallen asleep on. For nearly three decades, East Germans would be kept behind this barrier, the Berlin Wall.
See full article: The Rise and Fall of the Berlin Wall