Berlin is the capital city of Germany. It is also the biggest city in Germany. About 3,700,000 live there . 
The city is in the eastern part of Germany. It is about 70
km (43.50 mi) west of Poland. Berlin has an area of 891 km (344.02 2 sq mi). The rivers Havel, Dahme and Spree run through Berlin. It has an oceanic climate.
Berlin is home to many famous buildings and monuments, like the
Siegessäule, the Brandenburger Tor, the Reichstag and the boulevard Unter den Linden. On the boulevard are the Humboldt University and the State Opera of Berlin. The Governing Mayor of the city is Michael Müller ( SPD).
Berlin is a
world city of culture, politics, media and science . There are a lot of technology companies in the city. They are important for the city's  economy. Many planes and trains travel to and from Berlin because the city is an important place for tourism and business . 
Berlin is an important city for the history of Germany. The King of Prussia and the Emperor of Germany lived in Berlin. The government of Germany was in Berlin for many years. Bombs destroyed many buildings in the city in
World War Two. The city was split into West Berlin and East Berlin after World War Two. After the Berlin Wall was built in 1961 very few people were allowed to cross from East Berlin into West Berlin. The wall divided the city until 1989 when the East German government decided to allow anyone to cross, and people decided to destroy the wall.
map of the berlin boroughs
In 2001 the 23 boroughs of Berlin were changed into 12
1244 The first writings about a place called Berlin.
1451 The Hohenzollern family moved to Berlin as the place to rule their country
1618 – 48 After the Thirty Years' War in Germany, the number of people that lived in Berlin dropped to only 6000.
1701 Berlin became capital of Prussia.
1709 Berlin and its neighbor city Cölln (not Köln/Cologne) are combined to form the new Berlin.
1806 The army of Napoleon Bonaparte moved into Berlin.
1871 Berlin became capital of the German Empire.
1920 The Old Berlin and some neighbour towns are combined into "Greater Berlin" (Groß-Berlin).
1945 The town is divided into four sectors, used by the allies of World War II. There is a Soviet Sector, an American Sector, a British Sector and a French Sector.
1949 After foundation of the two Germanies, the town is still divided. There is now West Berlin and East Berlin.
1961 The Berlin Wall was built by the communist government of East Germany between the two halves of Berlin.
1990 After German reunification, the Berlin Wall is torn down, and there is only one Berlin again. The new Berlin becomes the capital of one Germany.
International Congress Center
Berlin Zoo, Polar bear cub "Knut" 24.03.2007
Buddy Bear has become an unofficial ambassador for Germany and is a symbol of Berlin.
Technical University Berlin
Nefertiti at the Egyptian Museum
Berlin has partnerships with 17 cities.
Each of the 12 boroughs also has their sister cities, sometimes called twin cities. 
United States, , (1967) Los Angeles
France, , (1987) Paris
Spain, , (1988) Madrid
Turkey, , (1989) Istanbul
Russia, , (1990) Moscow
Poland, , (1991) Warsaw
Hungary, , (1991) Budapest
Belgium, , (1992) Brussels
Indonesia, , (1993) Jakarta
Uzbekistan, , (1993) Tashkent
Mexico, , (1993) Mexico City
China, , (1994) Beijing
Japan, , Tokyo Japan, (1994)
Argentina, , (1994) Buenos Aires
Czech Republic, , (1995) Prague
Namibia, , (2000) Windhoek
United Kingdom, , (October 2000) London
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NOTES: 1. Geographically mostly in Asia.