Twietenkieker
From the homepage:
"Hamburg is also the perfect city for cycling! Due to my special knowledge as urban planner, I know the best routs for travelling. Travelling by bicycle allows us to visit larger areas of the city, but without loosing contact to the interesting details along the wayside, which you will miss for sure on a bus tour. The program of cycle tours (Stadtrundfahrten mit dem Rad) includes tours like "the middle of Hamburg" (Hamburgs Mitte), which combines the visit of the city centers of old Hamburg and of the previously Danish city of Altona."