Thanks for your answer!
For our next trip to the Kiel-Canal we will choose again for Burg, I quess.
The advantage of Burg is the ferry, it's very easy to cross the canal, so you don't have problems with photographing against the sun. After that, it's not far away from the Grünental-bridge, also a perfect place for photographing.
But, I keep Rendsburg in mind, you never know
