The story of Berlin is the story of its people, a people largely composed of succesive waves of immigrants. Dutchmen, Frenchmen, Hugenots, Jews, Italians, Poles, Scots, Silesians, Galicians, Saxons, Pomeranians, Prussians, Lithuanians, Russians, and God knows what else - rucksack Berliners, they were called - all poured in to what was for a long time little more than a malodorous garrison town. There, they were transformed by the Berliner Luft, the special Berlin atmosphere, into something rich and strange. It has been said that no-one is born a Berliner, everyone has to become one. You breathe in the air, which has been described as being addictive as cocaine or alcohol, and tune in to the fast Berliner Tempo, and are transfigured. - Berlin, by Anthony Read and David Fisher
Berlin is situated in what, in some historical accounts of the 12. century or so, is referred to as the "occupied territories" or "colonial" areas. Areas east of the Elbe and Saale had previous to this been inhabitated by Slavs. The Germans pushed east and displaced these Slavs, although many placenames in this region remain of Slavic origin. Berlin was a fishing village (at most) during the Slav period and it is easy to believe that the name is Slavic when pronounced in the proper way.
Berlin was originally the name of a village (later town) on the eastern bank of the Spree (the present-day Nikolaiviertel), which in its early German history had some sort of twin status with Coelln, on the other bank of the Spree, on the Spreeinsel. It would be too confusing here to go into when and how the name Berlin was applied to the whole area. (It is ironic that Berlin was a minor settlement midway between the important fortress towns of Spandau and Köpenick - nowadays Spandau and Köpenick effectively mark the western and eastern limits of the city of Berlin)
To cut a long story short....
By around 1650 (just after the Thirty Years War, when it is convenient too start a history of Berlin, by virtue of the fact that nothing too much happened before this), Coelln was the site of an important castle, or residence, of the Elector of Brandenburg.
In the next century, Brandenburg became Prussia, a powerful independent state and Berlin became the capital of this state. Its main buildings were extended westwards from the castle, along the Unter den Linden. Berlin grew bigger and it was enclosed by a new wall, the gate at the western end of the Linden being called the Brandenburg Gate.
Berlin's importance grew with Germany's growing importance, and in 1871 it became the capital of a new united Germany. This proved the trigger for a massive program of building to the west of Berlin. At this time, although the walls had been demolished, the Brandenburg Gate still remained standing, and this effectively marked the western limit of the city. The new areas in the west were brought into the city when Greater Berlin was created in 1920.
Joseph Goebbels, Nazi Party boss of Greater Berlin for 19 years, despaired of Berliners. He thought them rude, cynical, churlish and were not German thoroughbreds, but mongrels set down in the bleak, sandy Prussian plain, only too ready to bite the hand of anyone who tried to stroke them. - ( Berlin, by Anthony Read and David Fisher )
A Babylon amid the northern steppes - Konrad Adenauer
It is a new city, the newest I have ever seen. Chicago would seem venerable beside it. The next factor that strikes one is the spaciousness, the roominess of the city. There is no other city, in any country, whose streets are so generally wide. Only parts of Chicago are stately and beautiful, whereas all of Berlin is stately, and it is not merely in parts but uniformly beautiful - Mark Twain, about 1890.
A melting pot of everything that is evil - prostitutes, drinking-houses, cinems, Marxism, Jews, Strippers, negroes dancing, and all the vile offshoots of so-called "modern art". - Nazi Party newspaper, 1928