A very popular route for European tourists. Hamburg is one of the most interesting cities in Germany with a fascinating history and a very modern feel.
The journey to Brussels is not particularly scenic so take a few good books!
The Daytime service uses the Premium ICE and Thalys trains so reservations are compulsory and supplements payable. The night train would also be included on your pass with a supplement payable. You can book your seats at the station in Hamburg, try to stop at one of the many cafes for a pretzel whilst there!