3. The DDR Museum (Station: U2, U5, U8: Alexanderplatz)
The history of a split Berlin is visible at a glance of the architecture in Berlin, but the culture of the former East Berlin has rapidly been replaced with the usual western, pro-consumerism capitalism that we all are familiar with. The DDR Museum opened in 2006 as a private museum, and is a very interesting slice of East German culture. Part of the museum consists of the usual exhibits on the macro-political conflicts and the Berlin wall, but a good portion of the museum is devoted to nothing more than the everyday life of an East German. And that is fascinating.
Some of the best travel experiences come from the most mundane places which are tied into the daily lives of the people that live there. The supermarket, for example, will tell you far more about the daily experiences of the city's residents than a monument ever will and the DDR museum succeeds exactly on that level. There are genuine everyday artifacts from the DDR, like the horribly plastic "jeans" that were sold or the "coffee mix" (shown below) which must have been part of the daily routine for many living in East Berlin. Imagine waking up and brewing a strong cup of this!
Of course, if you are looking to learn about the politics and social program of the DDR, all of that is on display here to. The exhibits are engaging, interactive, and vary in their approach to letting the visitor explore the question. Even if this is in the touristy core, this is a great museum to visit and spend a few hours!