If you're looking for the epitome of "Hipster Berlin," you can't find anyplace more suitable than Mein Haus am See. In the most hip area of Mitte, Rosenthaler Platz, the cafe is more than just a coffee spot. It's also a bar and club. During the day, you'll see locals working on their laptops or drawing in sketchbooks, but when dusk starts to settle, the lights will dim and usually a DJ will be setting up the sound system.
Get a seat in the back of the stadium benches and watch time just pass by. As an added bonus: Mein Haus am See offers free Wi-Fi and is open 24 hours!