Sure — Checkpoint Charly, Siegessäule and the Brandenburg Gate are compulsatory for any visitor to Berlin. But if you want to see what makes Berlin the indisputable subcultural capital of Germany you should throw a glance behind the curtain of the travel brochures.
What makes the cultural Berlin so diverse is its role during the time of the division of Germany. Especially in the years between 1961 and 1989, where the western and eastern part of the city were divided by the Berliner Mauer, both parts emerged differently. While the isolated western part of the city shaped up to an appealing destination to countless youngsters wanting to escape the smugness of their West German hometowns, the eastern part was centrally formed to be a showcase of the superiority of command economy.
The lifestyle in the western part of Berlin, especially in the seventies and eighties was avant-garde. Berlin was one of the few cities in Germany having residential communities, alternative youth centres and a confident student movement.
Some of the most commendable insider tips to Berlin visitors emerged in that time. Kreuzberg, the district of choice for students, artists and anyone preferring cheap housing, played a key role for west Berlin back in the days.
If you're in Berlin in summer and like swimming you should check out Sommerbad Kreuzberg, commonly known as Prinzenbad. Don't expect a quiet afternoon though. The Prinzenbad is Berlin at its livliest. But an hour on the big sunbathing area will teach you more about the Berliners rough charm, humour and behaviour than any guidebook could.
A remarkable book about Berlin in the eighties is Berlin Blues by Sven Regener. It is about the life of 30 year old Herr Lehman (Mr. Lehmann) in western Berlin, who is working as a bartender in Kreuzberg district. Berlin Blues on amazon.com
Word has got around that Kreuzberg has a special atmosphere. That changed some areas of the district so much that they rather resemble the consumptive character of an amusement park then creative and recreative retreats nowadays. Especially famous Bergmannstraße, Yorckstraße and the area around Kottbusser Tor lost their authenticity in favour of expensive Latte-Macchiatos and Mochitos.
Fortunately the working-class district Neukölln, pervaded by the mouldy shopping streets Hermannstraße, Karl-Marx-Straße and Sonnenallee, isn't far. Traditional "Eckkneipen" (working-class pubs) are worth a visit. If you're in for a traditional Neukölln evening order Berliner Kindl, a Pilsener brewed in Neukölln since 1872, or the popular Neukölln-drink Futschi ("Chantré" Brandy with Coke).
If you're not into the tiddly atmosphere of speakeasies and want to go out for a drink in Neukölln anyway, you should visit Reuterkiez, the area around Weserstraße, Reuterstraße and Pflügerstraße next to the subway station Hermannplatz, with its popular pubs mostly frequented by students.
Berlin has several theaters. The most popular are Deutsches Theater, Berliner Ensemble (founded by Berthold Brecht) and Maxim Gorki Theater. If you're looking for typical Berlin stories performed you should think about visiting Prime Time Theater in Wedding (Müllerstraße 163b). Wedding is a district in the north of Berlin. Prime Time Theater exists since 2003 and features the popular programme Gutes Wedding — Schlechtes Wedding about the adventures of postman Kalle, kebab shop owner Mahmud, placement officer Frau Schinkel and many more unique Berlin characters.
For serious nightlife though there's no way around the districts of Mitte and Prenzlauer Berg. Especially in summer the streets around Schönhauser Allee and Danziger Straße resemble dancefloors. Not for nothing Berlin is reckoned as moving spirit in terms of electronic music throughout Europe.
An often forgotten fact is that Berlin is a city high in green spaces. The Großer Tiergarten in the heart of Berlin is four times bigger then Hyde Park in London and even displaces Central Park in New York. Most streets in Berlin are lined with trees. The huge nature reserves around Müggelsee in the south-east and Grunewald in the south-west are great opportunities to spend warm summer days.
Last but not least attention is invited to the sourroundings of Berlin. Owing to the fact that western Berlin was sourrounded by the wall, housing often ends abbrupt at the former borderline. That makes it easy to escape the city for the beautiful woods and lakes around Berlin.