Germany: Castle Tower in Düsseldorf

On Monday I got two postcards from Germany.

One of them shows the Castle Tower (on the right) in Düsseldorf. The Castle Tower is the only surviving part of the Düsseldorf Castle. Since 1984 it houses a maritime museum. 

Stamp:
100th birthday of Heinz Sielmann (issued 08-06-2017)

Thank You very much Marcel!