I need to book a wedding ceremony in Berlin.
The Reichstag, the Brandenburg Gate, Under den Linden and the TV tower on its eastern side, Kurfurstendamm on its western side & the KaDeWe super department store (particularly the top floor with its food hall). Potsdamer Platz, the centre of Berlin before the war, is a shopping and entertainment mecca http://www.potsdamerplatz.de/en.html
Berlin is a historians Mecca. Off Under den Linden you have the street where the centre of nazi power was with its teutonic looking buildings. Try finding Hitlers bunker if you can, but really you would probably be better off with a guide for that one. A tourist office by the Brandenburg date can give you different pictured maps for self guided themed walks. The Nazi era is one, the Cold War walk, more to the east of the city is another. Checkpoint Charlie should be visited as should the graffitti strewn remnants of the Berlin Wall. The Jewish Musemn, beautifuuly designed, is very interesting. To the east of the city off the end of Under den Linden you can find the old Jewish quarter with its beautiful synagogue and sad remnants of what was once a thriving rich Jewish community. If you can handle it, though very harrowing, you can take a trip 35km north of the city to Oranienburg to the concentration camp of Sachsenhausen, though it might not be the ideal trip for a honeymoon. Furthermore to the west of the city you can take a trip to a beautiful villa in a nice neighbourhood on the shores of Wannsee. However nothing nice happened here, it was where the Final Solution was decided, signed & sealed. While walking up the driveway is an experience, the inside is nothing like it was, given over to a musemn of flip boards (if that's the correct term) of what went on there etc. It was more the experience of being there more than anything & walking in the footsteps of such evil in such a beautiful innocuous setting.
On a lighter side there is the wonderful parkland in the centre of Berlin with its beautiful statues near the Reichstag & the old Olympic Stadium. Well worth a day trip is the suburb of Potsdam to the west of the city with its beautiful palaces & Spandau, famous for its prison. See http://www.visitberlin.de/ about almost 10 years ago