Other activities & things to do
Since I obviously haven't given you enough suggestions already, here's a few more.
Trabi Safari
You can actually go on a guided tour around Berlin behind the wheel of one of East Germany's horrible, clunky, slow and smelly Trabant cars, if that's your thing. Thankfully, the only people driving these around Berlin nowadays are the tourists doing the Trabi Safari.
S1, S2, S25, U2 - Potsdamer Platz
Do a river cruise
There are countless different cruises down the River Spree to choose from. This is a way to see Berlin from a different angle, at a slower and more relaxed pace.
Berlin Zoo & Tierpark
Berlin does have a zoo, as well as an animal park (Tierpark). I've never been to either as I didn't come to Berlin to see animals I can see in any other zoo around the world, but perhaps it's a good place to take kids. As far as I can tell, the only real difference is that the Tierpark is bigger but draws a smaller crowd.
Berlin Zoo: S5, S7, U2, U9 - Zoologischer Garten
Visit a lake
There are lots of lakes around the outskirts of Berlin which are very popular on weekends with Berliners who go to swim, have picnics/barbecues, play sports or just relax in the sun. I was at
Schlachtensee last weekend and there were a lot of people, probably because it was a Saturday and a really hot day. Other good ones include
Wannsee and
Strausssee. (You have probably worked out that "See" means lake in German.) I've heard that you can also take a ferry across the lake at Wannsee. Oh, and be warned that some lakes (and parks for that matter) are popular with nudists. (I'll let you decide whether or not you think that's a good thing.)
Schlachtensee: S1 - Schlachtensee
Wannsee: S1, S7 - Wannsee
Strausssee: S5 - Strausberg Stadt
Have a drink at the KaDeWe
I probably should have included this in the restaurant/bar/cafe section, but anyway... the Kaufhaus des Westerns (KaDeWe for short - pronounced car-day-vay) is the largest department store in Europe. Even I find it quite impressive. On the top floor is a very nice buffet and bar, and if you can get a table by the window the views are great. It's a nice spot to have lunch, but it's also quite expensive, so maybe just go for a drink or dessert in the afternoon.
U1, U2, U3 - Wittenberg Platz
Do a pub crawl
Berlin is famous for its nightclubs, so this is a bit of a no-brainer if you're into that kind of thing. There are plenty to choose from, I'm not going to recommend any particular one.
See a German comedy show
Ok, I'm not sure I would really recommend this to a non-German-speaking person, or even a German-speaking person, but I decided to see a stand-up comedy show in German at the
Quatsch Comedy Club one night and it was an unforgettable experience. The Germans are renowned for their lack of sense of humour, so I thought it would be funny to watch German comedians attempting to entertain an audience of Germans. It was. But it was so bad it was almost good.
S5, S7, U6 - Friedrichstr.
See a concert at the Berliner Philharmonie
For much classier entertainment, see a concert at the Berlin Philharmonic Centre.
S1, S2, S25, U2 - Potsdamer Platz