If you're in town on a Sunday there's no excuse, you have to get up very early to visit the Fishmarkt, one of Hamburg's most characteristic attractions.
From March to November it starts at 5 in the morning, the rest of the year at 7, and ends at 9:30 when the closing bell rings. In addition to the fish stalls, in this huge and fun market, you can buy clothes, fruit and more or less any other merchandise. Try the brunch that takes place in the historic fish auction hall where you can tap beer from early in the morning and listen to live music while dancing like crazy. Don't be put off by waking up early, it's so worth it!