Yeah, if you're interested in architecture, this is pretty nice - except it's raining when those steelplates on the floor become slippery... I learned in my studies the nice word "Unort" which might be translated into "Notplace" and in fact Potsdamer Platz is something like this. But it gets very interesting if you listen to Einstürzende Neubauten (babelfish translates it to: collapsing new buildings - lol) while talking a walk there.
If it comes to architecture you'll maybe enjoy the buildings around Unter den Linden, mostly from the time of Kaiser Wilhelm (19th century). These are very "heavy" buildings and fit perfectly into the mind of the prussian
- but I have to repeat you should go to Jewish Museum if you like to see some really nice modern architecture.
There are a couple of palaces and gardens (geobob mentioned Sanssouci already) like the Charlottenburger Schloss, which keeps the Collection Berggruen, some Picassos and Paul Klee - nice pieces there. Lately many small galleries appeared, some more, some less interesting. Berlin has a small but growing art-culture, mostly mixed stuff, often political. There are many political exhibitions, Berlin has a very intense history (Checkpoint Charlie, Berlin Museum, two StaSi exhibitions, Topographie des Terrors) and lots of (political) theatres in the eastern part.
I wouldn't suggest to go to the Zoo, cause it's crowded, but it has some really nice animals and is interesting you want to take pictures of them. Either you should go to Tierpark (Friedrichsfelde) which is in the east, huge and has some cute small elephants since last years or you go to the Aquarium (next to the Zoo) - one of the best I have seen so far.
Ah and Yes, Nightlife - there is.