Hamburg is definitely my favourite city in Germany. I must admit I love several German cities (I have a weakness for Germany!), their squared easy way of doing, their "fachwerk" houses, their cathedrals and why not... the German beer!
Hamburg offers several faces of the same city: Take a boat around the Alster and look at the amazing houses around, go to the "sex streets" at the Repperbahn & Sankt Pauli, walk around the "Altstadt" (Old City) and see famous architectural buildings. The most well-known are probably the Chilehaus (Chile House) and the Kontorhäuser (Office Buildings) at Burchardplatz but also Sprinkenhof, Mohlenhof and Messberghof...
Raven is one of the coolest places to be seen by now, unfortunately the service is far away of what is to be expected. Food good, but I did not enjoy a good experience there.
Le ciel, greatest views on the roof of Hotel Le Méridien, tasting menu not to be missed
Ratskeller below the Rathaus (city hall), typical German food in a higher niveau