<human>:  What is the history of the Berlin Wall?
<bot>: The Berlin Wall was a barrier built by East Germany in 1961 to separate East Berlin from West Berlin. Construction of the wall was officially started on August 13, 1961 and ended on November 9, 1989. The wall cut off West Berlin from neighbouring East Germany, including East Berlin, and divided the city and German society for more than 28 years. The construction of the wall put an end to the period of multi-party democracy in the area, as well as land, goods, and people movements between East and West Berlin. The fall of the wall and the reunification of Germany came with the collapse of the Soviet Union and the Eastern Bloc in 1989. Since German reunification in 1990, the wall has become a symbol of the Cold War.